Nikolai Olavi Czajkowski

• Fredriksen, Trude; Vatne, Torun Marie; Haukeland, Yngvild Bjartveit; Czajkowski, Nikolai Olavi; Wakefield, Claire E. & Fjermestad, Krister Westlye (2024). Evaluation of Siblings’ Perceived Relationship Outcomes with Their Parents in an Open Trial of the SIBS Intervention for Children with Chronic Disorders. Journal of Child and Family Studies. ISSN 1062-1024. doi: 10.1007/s10826-024-02824-z.
• Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn Omar (2024). The Longitudinal Relationship Between Life Events and Loneliness in Adolescence: A Twin Study. Developmental Psychology. ISSN 0012-1649. doi: 10.1037/dev0001692.
• Ebad Fardzadeh, Haghish; Czajkowski, Nikolai Olavi; Walby, Fredrik Andreas; Qin, Ping & Laeng, Bruno (2024). Suicide attempt risk predicts inconsistent self-reported suicide attempts: A machine learning approach using longitudinal data. Journal of Affective Disorders. ISSN 0165-0327. 355, s. 495–504. doi: 10.1016/j.jad.2024.03.133.
• Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Sheehy-Skeffington, Jennifer; Vassend, Olav Mandt; Røysamb, Espen & Eftedal, Nikolai Haahjem [Vis alle 9 forfattere av denne artikkelen] (2024). The genetic underpinnings of right-wing authoritarianism and social dominance orientation explain political attitudes beyond Big Five personality. Journal of Personality. ISSN 0022-3506. doi: 10.1111/jopy.12921.
• Bjørndal, Ludvig Daae; Ebrahimi, Omid V.; Røysamb, Espen; Karstoft, Karen-Inge; Czajkowski, Nikolai Olavi & Nes, Ragnhild Bang (2024). Stressful life events exhibit complex patterns of associations with depressive symptoms in two population-based samples using network analysis. Journal of Affective Disorders. ISSN 0165-0327. 349, s. 569–576. doi: 10.1016/j.jad.2024.01.054.
• Kozlowski Mayerhofer, Lilian Juliane; Nes, Ragnhild Bang; Lan, Xiaoyu; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Røysamb, Espen (2023). Wellbeing and illbeing in women exposed to physical and sexual violence: A population based longitudinal study. OSF Preprints.
• Ebad Fardzadeh, Haghish; Nes, Ragnhild Bang; Obaidi, Milan; Qin, Ping; Stänicke, Line Indrevoll & Bekkhus, Mona [Vis alle 8 forfattere av denne artikkelen] (2023). Unveiling Adolescent Suicidality: Holistic Analysis of Protective and Risk Factors Using Multiple Machine Learning Algorithms. Journal of Youth and Adolescence. ISSN 0047-2891. 53, s. 507–525. doi: 10.1007/s10964-023-01892-6. Fulltekst i vitenarkiv
• Tsotsi, Stella; Goh, Shaun; Coplan, Robert J.; Bølstad, Evalill; Czajkowski, Nikolai Olavi & Smajlagic, Dinka [Vis alle 7 forfattere av denne artikkelen] (2023). Co-occurrence of internalizing difficulties and aggression in early childhood and risk of mental health problems in middle childhood. International Journal of Behavioral Development. ISSN 0165-0254. 47(5), s. 384–396. doi: 10.1177/01650254231187902. Fulltekst i vitenarkiv
• Ebad Fardzadeh, Haghish; Czajkowski, Nikolai Olavi & von Soest, Tilmann Martin (2023). Predicting suicide attempts among Norwegian adolescents without using suicide-related items: a machine learning approach. Frontiers in Psychiatry. ISSN 1664-0640. 14. doi: 10.3389/fpsyt.2023.1216791. Fulltekst i vitenarkiv
• Ebad Fardzadeh, Haghish & Czajkowski, Nikolai Olavi (2023). Reconsidering False Positives in Machine Learning Binary Classification Models of Suicidal Behavior. Current Psychology. ISSN 1046-1310. doi: 10.1007/s12144-023-05174-z. Fulltekst i vitenarkiv
• Ebad Fardzadeh, Haghish; Laeng, Bruno & Czajkowski, Nikolai Olavi (2023). Are false positives in suicide classification models a risk group? Evidence for “true alarms” in a population-representative longitudinal study of Norwegian adolescents. Frontiers in Psychology. ISSN 1664-1078. 14. doi: 10.3389/fpsyg.2023.1216483. Fulltekst i vitenarkiv
• Tesli, Martin Steen; Nesvåg, Ragnar; Haukvik, Unn Kristin Hansen; Gustavson, Kristin; Tesli, Natalia & Friestad, Christine [Vis alle 12 forfattere av denne artikkelen] (2023). Common genetic and environmental risk for personality disorders and psychotic-like experiences in young adult twins. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 148(6), s. 561–569. doi: 10.1111/acps.13596. Fulltekst i vitenarkiv
• Torgalsbøen, Anne Kari; Mohn, Christine; Larøi, Frank; Fu, Susie & Czajkowski, Nikolai Olavi (2023). A ten-year longitudinal repeated assessment study of cognitive improvement in patients with first-episode schizophrenia and healthy controls: The Oslo Schizophrenia Recovery (OSR) study. Schizophrenia Research. ISSN 0920-9964. 260, s. 92–98. doi: 10.1016/j.schres.2023.08.008. Fulltekst i vitenarkiv
• Bjørndal, Ludvig Daae; Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi & Røysamb, Espen (2023). The structure of well-being: a single underlying factor with genetic and environmental influences. Quality of Life Research. ISSN 0962-9343. 32, s. 2805–2816. doi: 10.1007/s11136-023-03437-7.
• Rosenström, Tom H.; Czajkowski, Nikolai Olavi; Solbakken, Ole Andre & Saarni, Suoma E. (2023). Direction of dependence analysis for pre-post assessments using non-Gaussian methods: a tutorial. Psychotherapy Research. ISSN 1050-3307. doi: 10.1080/10503307.2023.2167526.
• Mylläri, Sanna; Saarni, Suoma Eeva; Ritola, Ville; Joffe, Grigori; Stenberg, Jan-Henry & Solbakken, Ole Andre [Vis alle 8 forfattere av denne artikkelen] (2022). Text Topics and Treatment Response in Internet-Delivered Cognitive Behavioral Therapy for Generalized Anxiety Disorder: Text Mining Study. Journal of Medical Internet Research. ISSN 1438-8871. 24(11). doi: 10.2196/38911.
• Oftedal, Aurora; Bekkhus, Mona; Haugen, Guttorm Nils; Hjemdal, Odin; Czajkowski, Nikolai Olavi & Kaasen, Anne (2022). Long-Term Impact of Diagnosed Fetal Anomaly on Parental Traumatic Stress, Resilience, and Relationship Satisfaction. Journal of Pediatric Psychology. ISSN 0146-8693. 48(2), s. 181–192. doi: 10.1093/jpepsy/jsac085. Fulltekst i vitenarkiv Vis sammendrag

  Knowledge regarding the long-term psychological adjustment of parents to children with prenatal diagnosis of congenital malformation is scarce. The aim of this study is to examine traumatic stress trajectories, resilience, and relationship satisfaction among parents to children with prenatal diagnosis of a congenital malformation, and to compare this to a sample of non-affected parents. Methods A prospective longitudinal cohort study was conducted at a tertiary perinatal referral center. Ninety-three mothers and 80 fathers who received a diagnosis of fetal anomaly during obstetric ultrasound examination (study group), and 110 mothers and 98 fathers with normal ultrasound findings (comparison group), reported their traumatic stress at four timepoints during pregnancy (T1-T4), 6 weeks after birth (T5), and 10-12 years after birth (T6). Resilience and relationship satisfaction was reported at 10-12 years after birth. Results Parents to children with a congenital malformation experienced significantly elevated traumatic stress levels over time, compared with parents of children without congenital malformation. The difference between groups was largest acutely after diagnosis and remained significant 10-12 years after the birth of the child. Resilience and relationship satisfaction levels were similar in both groups. Conclusions Despite experiencing high levels of traumatic stress over time, parents to children with a congenital malformation reported resilience and relationship satisfaction at similar levels to non-affected parents. This suggests that despite ongoing long-term distress, parents are still able to maintain positive psychological coping resources.

• Waraan, Luxsiya; Siqveland, Johan; Hanssen-Bauer, Ketil; Czajkowski, Nikolai Olavi; Axelsdottir, Brynhildur & Mehlum, Lars [Vis alle 7 forfattere av denne artikkelen] (2022). Family therapy for adolescents with depression and suicidal ideation: A systematic review and meta–analysis. Clinical Child Psychology and Psychiatry. ISSN 1359-1045. s. 1–19. doi: 10.1177/13591045221125005. Fulltekst i vitenarkiv
• Oftedal, Aurora; Bekkhus, Mona; Haugen, Guttorm Nils; Czajkowski, Nikolai Olavi & Kaasen, Anne (2022). The impact of diagnosed fetal anomaly, diagnostic severity and prognostic ambiguity on parental depression and traumatic stress: a prospective longitudinal cohort study. Acta Obstetricia et Gynecologica Scandinavica. ISSN 0001-6349. 101(11), s. 1291–1299. doi: 10.1111/aogs.14453. Fulltekst i vitenarkiv
• Kendler, Kenneth S.; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted (2022). Ludvig Dahl's psychiatric genetic studies in his 1859 monograph: “Contribution to the knowledge of insanity in Norway”. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics. ISSN 1552-4841. 189(6), s. 177–184. doi: 10.1002/ajmg.b.32914. Fulltekst i vitenarkiv
• Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). The role of sense of coherence and loneliness in borderline personality disorder traits: a longitudinal twin study. Borderline personality disorder and emotion dysregulation (BPDED). ISSN 2051-6673. 9. doi: 10.1186/s40479-022-00190-0. Fulltekst i vitenarkiv
• Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). The relationship between life events and sense of coherence in adolescence. A longitudinal twin study. Journal of Research in Personality. ISSN 0092-6566. 99. doi: 10.1016/j.jrp.2022.104259. Fulltekst i vitenarkiv
• Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). Childhood Trauma and Borderline Personality Disorder Traits: A Discordant Twin Study. Journal of Psychopathology and Clinical Science. ISSN 2769-7541. 131(4), s. 365–374. doi: 10.1037/abn0000755.
• Vassend, Olav Mandt; Czajkowski, Nikolai Olavi; Røysamb, Espen & Nielsen, Christopher Sivert (2022). The role of neuroticism and pain in dental anxiety: A twin study. Community Dentistry and Oral Epidemiology. ISSN 0301-5661. doi: 10.1111/cdoe.12763. Fulltekst i vitenarkiv
• Eftedal, Nikolai Haahjem; Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Sheehy-Skeffington, Jennifer; Røysamb, Espen & Vassend, Olav Mandt [Vis alle 8 forfattere av denne artikkelen] (2022). Justice sensitivity is undergirded by separate heritable motivations to be morally principled and opportunistic. Scientific Reports. ISSN 2045-2322. 12. doi: 10.1038/s41598-022-09253-2. Fulltekst i vitenarkiv
• Sælid, Gry Anette; Czajkowski, Nikolai Olavi; Aarø, Leif Edvard; Andersen, John Roger; Idsøe, Thormod & Helleseter, Miguel Delgado [Vis alle 7 forfattere av denne artikkelen] (2022). Effects of a school-based intervention on levels of anxiety and depression: a cluster-randomized controlled trial of the MindPower program in ten high schools in Norway. BMC Psychology. ISSN 2050-7283. 10, s. 1–14. doi: 10.1186/s40359-022-00721-y. Fulltekst i vitenarkiv
• Waraan, Luxsiya; Mehlum, Lars; Rognli, Erling W.; Czajkowski, Nikolai Olavi & Villabø, Marianne (2021). Associations between insecure attachment styles to parents and suicidal ideation in adolescents with depression . Scandinavian Journal of Child and Adolescent Psychiatry and Psychology. ISSN 2245-8875. 9, s. 41–51. doi: 10.21307/sjcapp-2021-006. Fulltekst i vitenarkiv
• Glad, Kristin Alve; Stensland, Synne; Czajkowski, Nikolai Olavi; Boelen, Paul & Dyb, Grete Anita (2021). The Longitudinal Association Between Symptoms of Posttraumatic Stress and Complicated Grief: A Random Intercepts Cross-Lag Analysis. Psychological Trauma. ISSN 1942-9681. doi: 10.1037/tra0001087. Fulltekst i vitenarkiv
• Waraan, Luxsiya; Rognli, Erling W.; Czajkowski, Nikolai Olavi; Villabø, Marianne & Mehlum, Lars (2021). Effectiveness of attachment-based family therapy compared to treatment as usual for depressed adolescents in community mental health clinics. Child and Adolescent Psychiatry and Mental Health (CAPMH). ISSN 1753-2000. 15, s. 1–14. doi: 10.1186/s13034-021-00361-x. Fulltekst i vitenarkiv
• Askim, Kine; Czajkowski, Nikolai Olavi & Knardahl, Stein (2021). Exploring dynamic relationships between employees’ personalities and psychosocial work factors. European Journal of Work and Organizational Psychology. ISSN 1359-432X. 31(1). doi: 10.1080/1359432X.2021.1912016. Vis sammendrag

  The current study addresses the potentially dynamic relationship between employees’ personality and their working conditions. A six-year full-panel longitudinal study of employed individuals was used to test whether (I) task-related, (II) social and (III) organizational work factors contribute to change Big-Five personality traits over time and whether personalities change working conditions. Bivariate latent change score analyses were conducted on repeated-measures data (four waves) from 2356 Norwegian employees. The results showed that specific work factors pertaining to task-related and social characteristics (i.e. leadership) were associated with personality trait changes. Contrary to our expectations, none of the work factors predicted change in neuroticism and extraversion, and we offer several possible explanations for these findings. The results also showed that all personality traits may play an active role in shaping specific attributes of the work environment over time and thereby shed light on how employees’ working conditions emerge.

• Ulset, Vidar; Czajkowski, Nikolai Olavi; Staton, Sally; Smith, Simon C.; Pattinson, Cassandra & Allen, Alicia [Vis alle 8 forfattere av denne artikkelen] (2021). Environmental Light Exposure, Rest-Activity Rhythms, and Symptoms of Inattention and Hyperactivity: An Observational Study of Australian Preschoolers. Journal of Environmental Psychology. ISSN 0272-4944. doi: 10.1016/j.jenvp.2021.101560.
• Waraan, Luxsiya; Rognli, Erling W.; Czajkowski, Nikolai Olavi; Mehlum, Lars & Villabø, Marianne (2020). Efficacy of attachment-based family therapy compared to treatment as usual for suicidal ideation in adolescents with MDD. Clinical Child Psychology and Psychiatry. ISSN 1359-1045. doi: 10.1177/1359104520980776. Fulltekst i vitenarkiv
• Czajkowski, Nikolai Olavi; Kendler, Kenneth S; Torvik, Fartein Ask; Ystrøm, Eivind; Rosenström, Tom Henrik & Gillespie, Nathan [Vis alle 7 forfattere av denne artikkelen] (2020). Caffeine consumption, toxicity, tolerance and withdrawal; shared genetic influences with normative personality and personality disorder traits. Experimental and clinical psychopharmacology. ISSN 1064-1297. doi: 10.1037/pha0000429. Fulltekst i vitenarkiv
• Rognli, Erling W.; Aalberg, Marianne & Czajkowski, Nikolai Olavi (2020). Using informant discrepancies in report of parent–adolescent conflict to predict hopelessness in adolescent depression. Clinical Child Psychology and Psychiatry. ISSN 1359-1045. 26(1), s. 96–109. doi: 10.1177/1359104520969761. Fulltekst i vitenarkiv Vis sammendrag

  Hopelessness is an important symptom of adolescent depression, being associated with both risk of suicide and poor treatment response, but predictors of hopelessness are understudied. Conflict with parents is common in adolescent depression, but parents and adolescents often disagree when reporting conflict severity. Discrepancy in reporting may be an indicator of the parent–adolescent dyad lacking a shared representation of the state of their relationship. This could make conflicts seem unresolvable to the adolescent, leading to expectations of persistent stress and lack of support, increasing hopelessness. This study employed latent difference scores, ordinal regression and cross-validation to evaluate the hypothesis that discrepancy in report of parent–adolescent conflict would predict hopelessness among depressed adolescents. Parents reporting less conflict than the adolescent was associated with increased adolescent hopelessness, giving preliminary support to the hypothesis.

• Rognli, Erling W.; Waraan, Luxsiya; Czajkowski, Nikolai Olavi & Villabø, Marianne (2020). Moderation of treatment effects by parent-adolescent conflict in a randomised controlled trial of Attachment-Based Family Therapy for adolescent depression. Scandinavian Journal of Child and Adolescent Psychiatry and Psychology. ISSN 2245-8875. 8, s. 110–122. doi: 10.21307/sjcapp-2020-011. Fulltekst i vitenarkiv
• Eilertsen, Espen Moen; Hannigan, Laurie John; McAdams, Tom A.; Rijsdijk, Frühling V.; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Vis alle 8 forfattere av denne artikkelen] (2020). Parental Prenatal Symptoms of Depression and Offspring Symptoms of ADHD: A Genetically Informed Intergenerational Study. Journal of Attention Disorders. ISSN 1087-0547. doi: 10.1177/1087054720914386. Fulltekst i vitenarkiv
• Rosenström, Tom Henrik; Torvik, Fartein Ask; Ystrøm, Eivind; Aggen, Steven H.; Gillespie, Nathan A. & Krueger, Robert F. [Vis alle 9 forfattere av denne artikkelen] (2020). Specific Antisocial and Borderline Personality Disorder Criteria and General Substance Use: A Twin Study. Personality Disorders: Theory, Research, and Treatment. ISSN 1949-2715. 12(3), s. 228–240. doi: 10.1037/per0000404. Fulltekst i vitenarkiv
• Liu, Hang; Laeng, Bruno & Czajkowski, Nikolai Olavi (2020). Does stereopsis improve face identification? A study using a virtual reality display with integrated eye-tracking and pupillometry. Acta Psychologica. ISSN 0001-6918. 210. doi: 10.1016/j.actpsy.2020.103142. Fulltekst i vitenarkiv
• Glad, Kristin Alve; Czajkowski, Nikolai Olavi; Dyb, Grete & Hafstad, Gertrud Sofie (2020). Does event centrality mediate the effect of peritraumatic reactions on post-traumatic growth in survivors of a terrorist attack? European Journal of Psychotraumatology. ISSN 2000-8066. 11(1). doi: 10.1080/20008198.2020.1766276. Fulltekst i vitenarkiv
• Haukeland, Yngvild; Czajkowski, Nikolai Olavi; Fjermestad, Krister; Silverman, Wendy K.; Mossige, Svein & Vatne, Torun (2020). Evaluation of “SIBS”, An Intervention for Siblings and Parents of Children with Chronic Disorders. Journal of Child and Family Studies. ISSN 1062-1024. 29. doi: 10.1007/s10826-020-01737-x. Fulltekst i vitenarkiv
• Siegel, Marte Langenes; Binder, Eva Mathilde Gullestad; Dahl, Hanne-Sofie Johnsen ; Czajkowski, Nikolai Olavi; Critchfield, Kenneth L. & Høglend, Per Andreas [Vis alle 7 forfattere av denne artikkelen] (2020). Therapeutic Atmosphere in Psychotherapy Sessions. International Journal of Environmental Research and Public Health (IJERPH). ISSN 1661-7827. 17(11). doi: 10.3390/ijerph17114105. Fulltekst i vitenarkiv Vis sammendrag

  There is uncertainty concerning what the active ingredients in psychotherapy are. The First Experimental Study of Transference interpretations (FEST) was a randomized controlled trial of the effects of transference work (TW) in psychodynamic psychotherapy. Women with low quality of object relations (QOR) showed a large positive effect of transference work, while men with high QOR showed a slight negative effect. The present study aimed to expand the knowledge from the FEST by investigating the therapeutic atmosphere with Structural Analysis of Social Behavior (SASB). Two-way ANOVAs were conducted to investigate differences between SASB cluster scores between subgroups. The therapeutic atmosphere was characterized by Protect-Trust, Affirm-Disclose and Control-Submit. Multilevel modeling was used to assess the relationship between a therapist variable and outcomes for men and women. Contrary to expectations, no significant differences in therapeutic atmosphere between subgroups (with or without TW in women with low QOR and men with high QOR) were observed using the process measure SASB.

• Gjerdevik, Miriam; Gjessing, Håkon K.; Romanowska, Julia; Haaland, Øystein Ariansen; Jugessur, Astanand & Czajkowski, Nikolai Olavi [Vis alle 7 forfattere av denne artikkelen] (2020). Design efficiency in genetic association studies. Statistics in Medicine. ISSN 0277-6715. 39, s. 1292–1310. doi: 10.1002/sim.8476. Fulltekst i vitenarkiv
• Rognli, Erling Wright; Waraan, Luxsiya; Czajkowski, Nikolai Olavi; Solbakken, Ole Andre & Aalberg, Marianne (2020). Conflict with Parents in Adolescent Depression: Associations with Parental Interpersonal Problems and Depressive Symptoms. Child Psychiatry and Human Development. ISSN 0009-398X. 51, s. 442–452. doi: 10.1007/s10578-020-00955-0. Fulltekst i vitenarkiv Vis sammendrag

  Conflict with parents is common among depressed adolescents, interferes with treatment, and may increase risk of recurrence. Parental depressive symptoms have been shown to predict conflict with adolescent children, but an important role for different kinds of parental interpersonal problems, as described by interpersonal circumplex, is also plausible. This study compared parental interpersonal problems to parental depressive symptoms as predictors of parent-adolescent conflict reported by a depressed adolescent child, using multilevel linear regression, leave-one-out cross-validation and model stacking (N = 100 parents, 57 mothers and 43 fathers, of 60 different adolescents). Cross-validation and model stacking showed that including parental interpersonal problems contributes to accurate predictions. Parents reporting more interpersonal problems related to excessive dominance or submissiveness was associated with increased or decreased conflict, respectively. Parental depressive symptoms were found to be negatively associated with parent-adolescent conflict only in father-adolescent relationships.

• Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Vassend, Olav; Røysamb, Espen; Eftedal, Nikolai Haahjem & Sheehy-Skeffington, Jennifer [Vis alle 8 forfattere av denne artikkelen] (2019). Correlations between social dominance orientation and political attitudes reflect common genetic underpinnings. Proceedings of the National Academy of Sciences of the United States of America. ISSN 0027-8424. 116(36), s. 17741–17746. doi: 10.1073/pnas.1818711116. Fulltekst i vitenarkiv
• Glad, Kristin Alve; Czajkowski, Nikolai Olavi; Dyb, Grete & Hafstad, Gertrud Sofie (2019). Cross-Lagged Association Between Symptoms of Posttraumatic Stress Disorder and Perceived Centrality of a Terrorist Attack. Clinical Psychological Science. ISSN 2167-7026. doi: 10.1177/2167702619873590. Fulltekst i vitenarkiv
• Biele, Guido; Gustavson, Kristin; Czajkowski, Nikolai Olavi; Nilsen, Roy Miodini; Reichborn-Kjennerud, Ted & Magnus, Per [Vis alle 8 forfattere av denne artikkelen] (2019). Bias from self selection and loss to follow-up in prospective cohort studies. European Journal of Epidemiology (EJE). ISSN 0393-2990. 34(10), s. 927–938. doi: 10.1007/s10654-019-00550-1.
• Ulset, Vidar; Czajkowski, Nikolai Olavi; Kraft, Brage; Kraft, Pål; Wikenius, Ellen & Kleppestø, Thomas Haarklau [Vis alle 7 forfattere av denne artikkelen] (2019). Are unpopular children more likely to get sick? Longitudinal links between popularity and infectious diseases in early childhood . PLOS ONE. ISSN 1932-6203. 14(9), s. 1–14. doi: 10.1371/journal.pone.0222222. Fulltekst i vitenarkiv
• Kendler, Kenneth S.; Aggen, Steven H.; Gillespie, Nathan; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Reichborn-Kjennerud, Ted (2019). A twin study of cigarette and snus initiation and quantity of use in Norwegian Adult Twins. Twin Research and Human Genetics. ISSN 1832-4274. 22(2), s. 108–113. doi: 10.1017/thg.2019.9. Fulltekst i vitenarkiv
• Torvik, Fartein Ask; Rosenström, Tom Henrik; Gustavson, Kristin; Ystrøm, Eivind; Kendler, Kenneth S. & Bramness, Jørgen Gustav [Vis alle 8 forfattere av denne artikkelen] (2019). Explaining the association between anxiety disorders and alcohol use disorder: A twin study. Depression and Anxiety. ISSN 1091-4269. 36(6), s. 522–532. doi: 10.1002/da.22886. Fulltekst i vitenarkiv
• Kendler, Kenneth S.; Aggen, Steven H.; Gillespie, Nathan; Krueger, Robert F.; Czajkowski, Nikolai Olavi & Ystrøm, Eivind [Vis alle 7 forfattere av denne artikkelen] (2019). The structure of genetic and environmental influences on normative personality, abnormal personality traits, and personality disorder symptoms. Psychological Medicine. ISSN 0033-2917. 49(8), s. 1392–1399. doi: 10.1017/S0033291719000047. Fulltekst i vitenarkiv
• Fu, Susie; Czajkowski, Nikolai Olavi & Torgalsbøen, Anne-Kari (2019). Cognitive, work and social outcomes in fully recovered first-episode schizophrenia: On and off antipsychotic medication. Psychiatry. ISSN 0033-2747. doi: 10.1080/00332747.2018.1550735.
• Rosenström, Tom Henrik; Czajkowski, Nikolai Olavi; Ystrøm, Eivind; Krueger, Robert F; Aggen, Steven H & Gillespie, Nathan A [Vis alle 9 forfattere av denne artikkelen] (2019). Genetically Informative Mediation Modeling Applied to Stressors and Personality-Disorder Traits in Etiology of Alcohol Use Disorder. Behavior Genetics. ISSN 0001-8244. 49(1), s. 11–23. doi: 10.1007/s10519-018-9941-z. Fulltekst i vitenarkiv
• Czajkowski, Nikolai Olavi; Aggen, Steven H.; Krueger, Robert F; Kendler, Kenneth S.; Neale, Michael C. & Knudsen, Gun Peggy [Vis alle 10 forfattere av denne artikkelen] (2018). A Twin Study of Normative Personality and DSM-IV Personality Disorder Criterion Counts: Evidence for Separate Genetic Influences. American Journal of Psychiatry. ISSN 0002-953X. 175(7), s. 649–656. doi: 10.1176/appi.ajp.2017.17050493.
• Knutsen, Marie Lindebø; Czajkowski, Nikolai Olavi & Ormhaug, Silje Mørup (2018). Changes in posttraumatic stress symptoms, cognitions, and depression during treatment of traumatized youth. Behaviour Research and Therapy. ISSN 0005-7967. 111, s. 119–126. doi: 10.1016/j.brat.2018.10.010.
• Rosenström, Tom Henrik; Gjerde, Line C.; Krueger, Robert Frederick; Aggen, Steven H.; Czajkowski, Nikolai Olavi & Gillespie, Nathan A. [Vis alle 10 forfattere av denne artikkelen] (2018). Joint factorial structure of psychopathology and personality. Psychological Medicine. ISSN 0033-2917. doi: 10.1017/S0033291718002982. Fulltekst i vitenarkiv
• Røysamb, Espen; Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi & Vassend, Olav (2018). Genetics, personality and wellbeing. A twin study of traits, facets and life satisfaction. Scientific Reports. ISSN 2045-2322. 8. doi: 10.1038/s41598-018-29881-x. Fulltekst i vitenarkiv
• Vassend, Olav; Røysamb, Espen; Nielsen, Christopher Sivert & Czajkowski, Nikolai Olavi (2018). Fatigue symptoms in relation to neuroticism, anxiety-depression, and musculoskeletal pain. A longitudinal twin study. PLOS ONE. ISSN 1932-6203. 13(6). doi: 10.1371/journal.pone.0198594. Fulltekst i vitenarkiv
• Fu, Susie; Czajkowski, Nikolai Olavi & Torgalsbøen, Anne-Kari (2018). Cognitive improvement in first-episode schizophrenia and healthy controls: A 6-year multi-assessment follow-up study. Psychiatry Research. ISSN 0165-1781. 267, s. 319–326. doi: 10.1016/j.psychres.2018.06.016. Fulltekst i vitenarkiv
• Gillespie, Nathan A.; Aggen, Steven H.; Gentry, Amanda E.; Neale, Michael Churton; Knudsen, Gun Peggy S. & Krueger, Robert Frederick [Vis alle 14 forfattere av denne artikkelen] (2018). Testing Genetic and Environmental Associations Between Personality Disorders and Cocaine Use: A Population-Based Twin Study. Twin Research and Human Genetics. ISSN 1832-4274. 21(1), s. 24–32. doi: 10.1017/thg.2017.73. Fulltekst i vitenarkiv
• Gillespie, Nathan A.; Aggen, Steven H.; Neale, Michael C.; Knudsen, Gun Peggy S.; Krueger, Robert F. & South, Susan C. [Vis alle 11 forfattere av denne artikkelen] (2018). Associations between personality disorders and cannabis use and cannabis use disorder: a population‐based twin study. Addiction. ISSN 0965-2140. 113(8), s. 1488–1498. doi: 10.1111/add.14209. Fulltekst i vitenarkiv
• Welander-Vatn, Audun; Torvik, Fartein Ask; Czajkowski, Nikolai Olavi; Kendler, Kenneth S; Reichborn-Kjennerud, Ted & Knudsen, Gun Peggy S. [Vis alle 7 forfattere av denne artikkelen] (2018). Relationships Among Avoidant Personality Disorder, Social Anxiety Disorder, and Normative Personality Traits: A Twin Study. Journal of Personality Disorders. ISSN 0885-579X. 33(3), s. 289–309. doi: 10.1521/pedi_2018_32_341. Fulltekst i vitenarkiv
• Torgalsbøen, Anne-Kari; Fu, Susie & Czajkowski, Nikolai Olavi (2018). Resilience trajectories to full recovery in first-episode schizophrenia. European psychiatry. ISSN 0924-9338. 52, s. 54–60. doi: 10.1016/j.eurpsy.2018.04.007. Fulltekst i vitenarkiv
• Rosenström, Tom Henrik; Torvik, Fartein Ask; Ystrøm, Eivind; Czajkowski, Nikolai Olavi; Gillespie, Nathan A. & Aggen, Steven H. [Vis alle 9 forfattere av denne artikkelen] (2018). Prediction of alcohol use disorder using personality disorder traits: a twin study. Addiction. ISSN 0965-2140. 113(1), s. 15–24. doi: 10.1111/add.13951.
• Øie, Merete Glenne; Hovik, Kjell Tore; Andersen, Per Normann; Czajkowski, Nikolai Olavi & Skogli, Erik Winther (2018). Gender differences in the relationship between changes in ADHD symptoms, executive function, and self- and parent-report depression symptoms in boys and girls with ADHD: A two-year follow-up study. Journal of Attention Disorders. ISSN 1087-0547. 22(5), s. 446–459. doi: 10.1177/1087054716664407.
• Torvik, Fartein Ask; Rosenström, Tom Henrik; Ystrøm, Eivind; Tambs, Kristian; Røysamb, Espen & Czajkowski, Nikolai Olavi [Vis alle 10 forfattere av denne artikkelen] (2017). Stability and change in etiological factors for alcohol use disorder and major depression. Journal of Abnormal Psychology. ISSN 0021-843X. 126(6), s. 812–822. doi: 10.1037/abn0000280. Fulltekst i vitenarkiv
• Fu, Susie; Czajkowski, Nikolai Olavi; Rund, Bjørn Rishovd & Torgalsbøen, Anne-Kari (2017). The relationship between level of cognitive impairments and functional outcome trajectories in first-episode schizophrenia. Schizophrenia Research. ISSN 0920-9964. 190, s. 144–149. doi: 10.1016/j.schres.2017.03.002. Fulltekst i vitenarkiv
• Rosenström, Tom Henrik; Ystrøm, Eivind; Torvik, Fartein Ask; Czajkowski, Nikolai Olavi; Gillespie, Nathan A. & Aggen, Steven H. [Vis alle 9 forfattere av denne artikkelen] (2017). Genetic and Environmental Structure of DSM-IV Criteria for Antisocial Personality Disorder: A Twin Study. Behavior Genetics. ISSN 0001-8244. 47(3), s. 265–277. doi: 10.1007/s10519-016-9833-z.
• Reichborn-Kjennerud, Ted; Krueger, R F; Ystrøm, Eivind; Torvik, Fartein Ask; Rosenström, Tom Henrik & Aggen, S H [Vis alle 11 forfattere av denne artikkelen] (2017). Do DSM-5 Section II personality disorders and Section III personality trait domains reflect the same genetic and environmental risk factors? Psychological Medicine. ISSN 0033-2917. 47(12), s. 2205–2215. doi: 10.1017/S0033291717000824.

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• Green Krogshus, Kristian; Bjertness, Espen; Czajkowski, Nikolai Olavi; Bang Nes, Ragnhild & Rodriguez-Cano, Ruben (2023). 5 Ways to Promote Wellbeing @School.
• Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen; Sunde, Hans Fredrik; Kleppestø, Thomas Haarklau; Ystrøm, Eivind & Czajkowski, Nikolai Olavi (2023). Correlations on Norwegian national standardized tests between millions of pairs of relatives: Exploring the impacts of assortative mating and parental effects.
• Smajlagic, Dinka; Tsotsi, Stella; Gjerdevik, Miriam; Page, Christian Magnus; Zayats, Tetyana & Austerberry, Chloe [Vis alle 14 forfattere av denne artikkelen] (2022). Parent-of-origin effects in childhood aggression.
• Prydz, Monica Beer; Czajkowski, Nikolai Olavi; Eilertsen, Maja & Nes, Ragnhild Bang (2022). Helsekompetansens kraft i folkehelsearbeidet. Hvordan kan helsekompetanse innlemmes i folkehelsearbeid?
• Prydz, Monica Beer; Czajkowski, Nikolai Olavi; Bang Nes, Ragnhild; Røysamb, Espen & Eilertsen, Maja (2022). Promoting wellbeing and preventing mental health problems: A randomized controlled trail of the Five Ways to Wellbeing Intervention .
• Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi; Røysamb, Espen & Eilertsen, Maja Gunvor (2022). Promoting wellbeing and preventing mental health problems: A randomized controlled trail of the Five Ways to All Intervention .
• Nes, Ragnhild Bang; Røysamb, Espen; Eilertsen, Maja Gunvor & Czajkowski, Nikolai Olavi (2022). Promoting Wellbeing using the Five Ways to Wellbeing framework .
• Eilertsen, Maja; Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi; Røysamb, Espen & Prydz, Monica Beer (2022). Promoting Wellbeing using the Five Ways to Wellbeing framework .
• Eilertsen, Maja; Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi; Røysamb, Espen; Ørstavik, Ragnhild & Vassend, Olav Mandt (2022). Effects of illness on wellbeing: A co-twin control analysis.
• Eilertsen, Maja; Nes, Ragnhild Bang; Prydz, Monica Beer; Røysamb, Espen & Czajkowski, Nikolai Olavi (2022). Bridging the gap - from research to practice.
• Tsotsi, Stella; Goh, shaun; Czajkowski, Nikolai Olavi; Smajlagic, Dinka; Coplan, Robert & Bølstad, Evalill [Vis alle 7 forfattere av denne artikkelen] (2022). The co-occurrence of emotional difficulties and aggression in early childhood and the risk of later mental health outcomes: The Norwegian Mother, Father and Child Cohort.
• Kozlowski Mayerhofer, Lilian Juliane; Nes, Ragnhild Bang; Lan, Xiaoyu; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Røysamb, Espen (2022). Social support and wellbeing across the pre- and postnatal period in women victim of abuse: Findings from the Norwegian Mother, Father and Child Cohort Study.
• Eilertsen, Maja Gunvor; Nes, Ragnhild Bang; Røysamb, Espen & Czajkowski, Nikolai Olavi (2022). Fem grep for økt Hverdagsglede på tvers av nivåer.
• Torgalsbøen, Anne Kari & Czajkowski, Nikolai Olavi (2022). Full recovery and self-efficacy in first episode schizophrenia: The OSR cohort at 10 year follow-up.
• Siegel, Marte Langenes; Binder, Eva Mathilde Gullestad; Dahl, Hanne-Sofie Johnsen ; Czajkowski, Nikolai Olavi; Critchfield, Kenneth L. & Høglend, Per Andreas [Vis alle 7 forfattere av denne artikkelen] (2020). Erratum: Therapeutic atmosphere in psychotherapy sessions. int. j. environ. res. public health 2020, 17, 4105. International Journal of Environmental Research and Public Health (IJERPH). ISSN 1661-7827. 17(14), s. 1–2. doi: 10.3390/ijerph17145241.
• Glad, Kristin Alve; Stensland, Synne; Czajkowski, Nikolai Olavi; Boelen, Paul & Dyb, Grete (2020). The longitudinal association between symptoms of posttraumatic stress and complicated grief. A random intercepts cross-lag analysis.
• Glad, Kristin Alve; Stensland, Synne; Czajkowski, Nikolai Olavi; Boelen, Paul & Dyb, Grete (2019). The longitudinal association between complicated grief and symptoms of posttraumatic stress. A random-intercept cross-lag analysis.
• Rognli, Erling W.; Villabø, Marianne & Czajkowski, Nikolai Olavi (2019). Discrepant Reports of Parent-adolescent Conflict is Associated with Hopelessness in Adolescent Depression.
• Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Vassend, Olav; Røysamb, Espen; Eftedal, Nikolai Haahjem & Kunst, Jonas R. [Vis alle 8 forfattere av denne artikkelen] (2019). Social dominance orientation has both genetic and unique environmental influences, but only genetic pleiotropy accounts for its correlation with political attitudes.
• Waraan, Luxsiya; Rognli, Erling W.; Mehlum, Lars; Czajkowski, Nikolai Olavi & Villabø, Marianne (2019). The efficacy of psychotherapy for suicidal ideation in youth.
• Waraan, Luxsiya; Rognli, Erling W.; Mehlum, Lars; Czajkowski, Nikolai Olavi & Villabø, Marianne (2018). The association between Attachment Style to Father and Suicidal Ideation in Adolescents with Depression. .
• Eilertsen, Espen Moen; Hannigan, Laurie John; McAdams, Tom A.; Rijsdijk, Fruhling; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Vis alle 8 forfattere av denne artikkelen] (2018). Parental prenatal depression and offspring ADHD: a genetically informed intergenerational study. Behavior Genetics. ISSN 0001-8244. s. 469–469.
• Eilertsen, Espen Moen; Hannigan, Laurie John; Mcadams, Tom; Rijsdijk, Fruhling; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Vis alle 8 forfattere av denne artikkelen] (2018). Parental prenatal depression and offspring ADHD: A genetically informed intergenerational study.
• Rosenström, Tom Henrik; Czajkowski, Nikolai Olavi; Ystrøm, Eivind; Krueger, RF; Aggen, Steven H. & Gillespie, Nathan A. [Vis alle 9 forfattere av denne artikkelen] (2017). Stressful life events, antisocial and borderline personality traits, and alcohol use disorder: a genetically informative mediation study.
• H. Kleppestø, Thomas; Czajkowski, Nikolai Olavi; Vassend, Olav; Røysamb, Espen; R. Kunst, Jonas & Thomsen, Lotte (2017). Preferring domination or egalitarianism: Genetic and environmental structure of Social Dominance Orientation.
• Czajkowski, Nikolai Olavi; Bang Nes, Ragnhild; Vassend, Olav & Røysamb, Espen (2017). Effects of somatic and mental illness on subjective well-being. A discordant twin analysis.
• Røysamb, Espen; Bang Nes, Ragnhild; Czajkowski, Nikolai Olavi & Vassend, Olav (2017). Anxiety, depression and life satisfaction after midlife. A twin study across 20 years.
• Bang Nes, Ragnhild; Czajkowski, Nikolai Olavi; Røysamb, Espen & Vassend, Olav (2017). Components and sources of well-being and ill-being: A twin study.
• Vassend, Olav; Nielsen, Christopher Sivert; Røysamb, Espen & Czajkowski, Nikolai Olavi (2017). Fatigue symptoms in relation to neuroticism, anxiety-depression, and musculoskeletal pain. A longitudinal study.
• Torvik, Fartein Ask; Rosenström, Tom Henrik; Czajkowski, Nikolai Olavi; long, elizabeth; Gillespie, Nathan A. & Reichborn-Kjennerud, Ted (2017). Results from a longitudinal twin study combining diagnostic interviews and registry data on personality, mental disorders, and substance use.
• Glad, Kristin Alve; Hafstad, Gertrud Sofie; Dyb, Grete & Czajkowski, Nikolai Olavi (2020). Transformed by trauma. A longitudinal study of posttraumatic stress, growth and perceived event centrality among youths and emerging adults after the terrorist attack on Utøya island . Damnett.
• Rognli, Erling W.; Villabø, Marianne & Czajkowski, Nikolai Olavi (2020). Conflict with Parents in Adolescent Depression. Universitetet i Oslo. ISSN 1504-3991. Fulltekst i vitenarkiv Vis sammendrag

  Adolescents who are depressed tend to have more conflictual relationships with their parents, and depression and parent-adolescent conflict is thought to have bidirectional association. In this thesis, results of three studies are presented that investigate how dysfunctional parent-adolescent conflict in adolescent depression is associated with parental characteristics, treatment outcome and clinical status, along with a narrative review of the literature on parent-adolescent conflict and adolescent depression in clinical and non-clinical samples.

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