Modafinil's Effects on Cognition in Remitted MDD

Background:

Major Depressive Disorder (MDD) is a chronic mental disorder with a lifetime prevalence of 5-20% (Kessler et al., 2003; Woo et al., 2016). While depressed mood and loss of interest in activities are core features of MDD, cognitive deficits such as indecisiveness and inattention are present and interfere with work and social functioning (McIntyre et al., 2013). These cognitive deficits frequently persist beyond remission from a Major Depressive Episode (MDE), with up to 94% of those impaired during an episode continuing to experience deficits after the episode (Bhalla et al., 2006), including deficits in attention, executive functioning, and psychomotor speed (Salagre et al., 2017). These residual cognitive symptoms often persist and are associated with poor functioning and loss of productivity (Lam et al., 2014).

In a systematic review examining MDD patients in remission, multiple regression analyses found that MDD predicted lower performance on measures of attention, processing speed, and cognitive flexibility relative to healthy controls (HCs; Hasselbalch et al., 2011). Further evidence for the presence of neuropsychological deficits in remitted MDD patients comes from a systematic review and meta-analysis that found the remitted MDD patient group had executive function and attentional deficits, while symptomatic patients exhibited executive function, attentional, and memory deficits (Roc et al., 2013).

Importantly, there are no medications with evidence to modify cognition in remitted depression. This suggests that in order to assist in the recovery of cognitive and functional abilities, additional novel treatment options are required.

There is considerable evidence that subjective and objective measures of cognition are not well correlated in MDD. This has informed the investigators' choice of separate subjective and objective measures for this study. In addition, cognitive disturbances affect psychosocial function and quality of life across several areas, and this necessitated measurement of quality of life. In this study, the investigators will use a computerized version of the Central Nervous System (CNS) Vital Signs Cognitive Battery, which will provide a Neurocognitive Index score (NCI). The NCI is a global measure of cognitive functioning, averaging the scores from 7 tests over 5 domains: composite memory, psychomotor speed, reaction time, complex attention, and cognitive flexibility.

Pilot results from the The Canadian Biomarker Integration Network in Depression (CAN-BIND)-1 study, involving treatment with escitalopram, have clearly documented the nature of deficits, and are in line with expectations in remitted depression. In this pilot sample of 208 participants, 15% of participants had global cognitive impairment despite 8 weeks of antidepressant treatment and achievement of clinical remission (McInerney, personal communication).

In an 8-week antidepressant study, those who significantly improved in global cognitive functioning (assessed using NCI) had superior functioning and work productivity relative to those who did not significantly improve (Hasselbalch et al., 2011). Vortioxetine is the only antidepressant with modest evidence for improving cognitive parameters during a depressive episode (Rock et al., 2013). Research into the use of psychostimulants as a treatment for cognitive deficits in depressed patients has led to the consideration of modafinil and methylphenidate as potential novel pharmacological treatments (Minzenberg et al., 2008). Modafinil is a well-tolerated wakefulness agent where only two clinical studies have previously examined its role on cognition in depression; one where currently depressed patients had improvements in one measure of executive function after 4 weeks of treatment as an adjuvant (DeBattista et al., 2004), and the other where there were improvements in memory after a single dose in depressed participants who achieved remission (Kaser et al., 2016). Unlike methylphenidate, modafinil appears to impact both "hot" (emotion-laden) and "cold" (independent of emotion) cognitive deficits, which are commonly seen in remitted depression.

Immediate effects of modafinil on cognition have been shown (Kaser et al., 2016) and the investigators will be the first to examine the pro-cognitive effects in a remitted depressed sample over 8 weeks. The dose of modafinil (200mg) used in the study, sample size, and randomized control trial (RCT) study design parallels those described in the immediate effect study, and this maintains continuity. However, the study does not examine whether the immediate effects are maintained. More importantly, it is unclear whether the cognitive improvements translate into improvement in functioning.

The added focus on functional outcomes fits with patient-centered models of healthcare, as functional outcomes are of greatest importance to most patients. Thus, the RCT study and choice of outcome variables have been carefully designed with specific endpoints to delineate these aspects. Cognitive flexibility, memory, and attention will be domains of importance in this study, since these domains have been shown in previous literature to be improved by modafinil (Minzenberg et al., 2008; DeBattista et al., 2004; Kaser et al., 2016).

Objectives, Hypotheses, and Impact:

The primary objective of this study is to delineate the cognitive effects of modafinil in patients with remitted depression at baseline and 4 weeks, and monitor whether these effects are maintained with continual dosage over an 8-week period. The secondary objective of this study is to understand the effect of modafinil in patients with remitted depression on measures of functioning at baseline, 4 weeks, and 8 weeks, and whether these effects parallel the cognitive changes.

The investigators' overarching hypothesis is that specific aspects of cognitive functioning, including the domains of memory, attention, and cognitive flexibility, will improve through treatment with modafinil. The investigators hypothesize that participants with remitted depression who continue to experience cognitive deficits and are taking modafinil will have improvements in aspects of cognitive domains at 4 weeks, and these improvements will be sustained at 8 weeks. It is also hypothesized that functional improvements will parallel the improvements in cognitive domains.

The study ensures a closer examination of modafinil's effect on individual facets of cognition in patients with remitted MDD. This enhanced understanding will enable the development of new treatment plans for residual cognitive symptoms, where none currently exist. Moreover, it could spur interest in new drug development programs to address an unmet need of targeting cognition across disorders where depression is a central feature (e.g. Bipolar Disorder, Generalized Anxiety Disorder). Finally, the study would delineate the specific endophenotypes within cognition (e.g. working memory) and functional improvement (e.g. social functioning), which would lead to personalized treatment options based on the endophenotype profile.

Methods In this randomized control trial, remitted MDD patients with residual cognitive deficits (n=50) will have cognitive symptoms and functioning evaluated before and after an 8-week trial of modafinil 200mg or placebo. Participants will be recruited through the ongoing CAN-BIND 1 Wellness Study; the Depression Program at St. Michael's Hospital; the shared care network at St. Michael's Hospital; and referrals from residents, family doctors, and other St. Michael's psychiatrists. All participants who meet inclusion criteria will be asked to enrol in this study and provide written informed consent.

Participants will be on a stable dose of an antidepressant for at least 6 months prior to enrolment. They will be required to remain on this stable dose for the duration (8 weeks) of the trial. They will be prescribed modafinil or placebo at a dose of 100 mg for the first week then 200mg for 7 weeks. After week 8, participants will be informed of which group they were in and if they were taking modafinil, they can choose to continue on modafinil or to discontinue.

Participants will undergo an 8-week randomized, placebo controlled treatment trial of modafinil 200mg with a total of 3 study visits. Participants may require more clinical visits as needed. Screening will be done to confirm study eligibility. At the screening visit all participants will provide demographic data (age, gender, education, ethnicity, occupation, family history of mental illness), undergo a structured diagnostic assessment (Mini-International Neuropsychiatric Interview), complete the CNS Vital Signs cognitive battery, and have the Montgomery-Asberg Depression Rating Scale administered. At the baseline visit, participants will initiate the study drug trial, complete clinician rated and self-report scales, and complete the cognitive battery in CNS Vital Signs. Participants will start with a 100 mg dose at baseline, and increase to the 200 mg dose at week 1 if the drug is well tolerated. Participants will repeat all measures at week 4 and 8. Adverse events will be recorded at each study visit. For participants who wish to discontinue the study drug at week 8, they will first have their dose decreased to 100 mg for one week and attend an additional week 9 safety visit to evaluate adverse events before full discontinuation of the study drug.