Depressed Mood Improvement Through Nicotine Dosing 3

The purpose of the Depressed MIND3 study is to determine whether blinded, placebo-controlled administration of transdermal nicotine results in significant cognitive, clinical and functional improvement in participants with LLD. Neuronal nicotinic receptors have long been known to play a critical role in memory function in preclinical studies, with nicotine improving attention, learning, and memory function. This may be particularly relevant in LLD, which is characterized both by affective symptoms and broad cognitive deficits. The co-occurrence of cognitive deficits in LLD is a clinically relevant phenotype characterized by significant disability and poor antidepressant response. Cognitive deficits can persist even with successful antidepressant treatment and increase the risk of depression relapse. Despite the clinical importance of cognitive deficits in LLD, there are no established treatments that specifically target cognition in this population. The lack of clear pharmacologic targets and therapies aimed at improving cognitive deficits in depression is a substantial deficiency in current therapeutics. We propose that modulation of the cognitive control network by stimulation of cholinergic system nicotinic acetylcholine receptors will improve both mood and cognition in depressed elders. The study is a randomized double blind placebo control trial that will enroll 80 participants over a 3-year period. Participants will be randomized (2:1) to receive either active transdermal nicotine (TDN) patches or matching placebo patches. Participants will apply patches daily for 12 weeks, followed by a 3-week taper period. The Aims of this blinded trial are to: 1) validate target engagement and determine whether change in brain activation to an emotional Stroop task is related to improvement in depression severity and cognitive performance; and 2) determine the specificity of TDN's effects by examining whether changes in the default mode network (DMN) or other regions occur with TDN and if so, are they related to change in clinical measures. AIM 1: Examine how TDN's neural circuit changes affect depressive symptoms in a blinded RCT. Hyp 1A: Compared with placebo, TDN administration will significantly reduce the Stroop BOLD response on functional Magnetic Resonance Imaging. This change will be associated with reduction in depression severity by the Montgomery-Asberg Depression Rating Scale (MADRS). Hyp 1B: Change in the Stroop BOLD response of other brain regions with TDN administration, specifically the DMN, will not be significantly associated with change in depression severity. Hyp 1C: Compared with placebo, TDN will improve depression severity measured by MADRS (primary clinical outcome), reduce apathy and rumination measured by self-report, and reduce negative self-referential thinking measured by the Trait Adjectives Task (secondary outcomes). AIM 2: Examine how TDN's circuit changes affect CCN-mediated cognitive performance. Hyp 2A: Reduction in the Stroop BOLD response will be associated with improvement in attention, working memory, and episodic memory performance. Change in the Stroop BOLD response of other regions, specifically the DMN, will not be associated with change in task performance. Hyp 2B: Compared with placebo, nicotine will improve performance on tasks of attention, working memory, and episodic memory (secondary outcomes).