Scientific abstract

Major depressive disorder (MDD) is a prevalent and debilitating condition associated with deficits across cognitive domains (e.g., speed of processing, attention, memory), including executive functions (EFs)—a set of higher-order cognitive processes necessary for goal-directed behavior. Deficits in EFs have a deleterious effect on functioning and hold proximal links with maladaptive emotional regulation strategies and depressive symptomatology. Importantly, such deficits often persist following remission, even when antidepressant medication treatment or psychotherapy has been provided. Cognitive remediation (CR) techniques—interventions aiming to improve cognitive functions, could accordingly prove useful in MDD. To date, CR has demonstrated moderate effectiveness for improving cognition, including EFs, in MDD, but the evidence of long-lasting effects that generalize to daily life are limited. Furthermore, there is little information available on which patients are likely to benefit from CR.

Goal Management Training (GMT) is a metacognitive strategy-based CR intervention to improve EFs through teaching compensatory strategies for application in daily life. The strategies aim to improve goal-directed behavior and increase executive control, with the hallmark feature of periodically stopping, monitoring performance, and employing a stepwise approach to problem-solving. Previous findings in neurological disorders and other neuropsychiatric samples indicate that GMT has the potential to produce long-term improvements in EFs that generalize to daily life, but the effectiveness has not been evaluated in MDD.

Executive functioning is difficult to operationalize and assess, and the clinical evaluation of EFs remains a challenge in MDD. As such, Paper I investigated the association between self-reported (subjective) everyday executive complaints, and performance on neurocognitive (objective) measures of EFs in depression. To provide information that could help identify patients in whom self-reported EFs are less likely to reflect performance on objective EF measures, the association of several characteristics (age, illness duration, IQ, depressive symptoms, rumination, and self-efficacy) with the discrepancy between subjective and objective measures was explored. Paper II aimed to evaluate the effectiveness of GMT for improving EFs and reducing depressive symptoms in an MDD sample with self-reported executive difficulties. The study utilized a single-blind randomized controlled trial (RCT) design comparing GMT with restorative drill-and-practice computerized cognitive training (CCT). The primary outcome was a rating scale pertaining to everyday EFs, and the primary endpoint was six months following treatment completion because the study aimed to assess the generalizability and durability of treatment effects. In Paper III, factors associated with long-term (six months) CR improvement were explored in a collapsed sample including both GMT and CCT participants. Completers of CR were categorized as “improvers” or “nonimprovers” in everyday EFs and in a neurocognitive measure of attention/EFs using reliable change index calculations. To gain insight into whether participants’ characteristics could help explain favorable treatment outcomes, improvers and nonimprovers were subsequently compared on various baseline variables (sociodemographic, psychological, illness-related, and neurocognitive).

Participants (Papers IIII) had received a diagnosis of mild-or-moderate MDD, and self-reported everyday executive complaints. Following a baseline assessment consisting of neurocognitive tests, rating scales of cognition, and mental health questionnaires, participants were randomized to nine sessions of either GMT (two hours, once a week, nine weeks) or CCT (one hour, twice a week, four to five weeks). Participants were reassessed upon treatment completion and six months post-treatment.

The findings from Paper I indicate that self-reported EF complaints and performance on neurocognitive measures of EFs are nonoverlapping in MDD. In addition, having a lower perceived self-efficacy, higher IQ, and a stronger tendency to ruminate were associated with “underestimation” of EFs (i.e., that participants rated their everyday executive functioning below what was evident from neurocognitive measures). These findings suggest that clinical evaluation of EFs in MDD should include both subjective and objective measures, and that underestimation of EF performance is associated with the respondent’s characteristics. Moreover, rumination and self-efficacy could represent potential treatment targets when aiming to correct underestimation of EFs or reduce everyday EF difficulties.

In Paper II, no significant between-group differences for any outcome (subjective EFs, objective EFs, depressive symptoms) emerged following treatment. However, exploratory within-group analyses identified long-lasting significant improvements in measures of subjective and objective EFs and depressive symptoms following GMT. The study provides preliminary evidence of generalized and durable effects of GMT in MDD, but at the same time, that the effectiveness is comparable to CCT.

In Paper III, no predictors of improvement following CR were identified. The findings suggest that neither of the investigated factors act as major barriers for CR improvement, and additionally that studies probably need to move beyond generic patients’ characteristics to identify reliable predictors that may improve CR effectiveness.

Publisert 23. sep. 2021 14:07 - Sist endret 23. sep. 2021 14:07