Late-life depression (LLD) is characterized both by affective symptoms and broad cognitive deficits. The co-occurrence of cognitive deficits in LLD, particularly executive dysfunction, 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. This is particularly important, as the cognitive deficits appear to directly contribute to disability and poor antidepressant treatment outcomes. The lack of clear pharmacologic targets and therapies aimed at improving cognitive deficits in depression is a substantial deficiency in current therapeutics.
Modulation of the cholinergic system by nicotinic receptor stimulation may improve both mood and cognition in depressed elders. Clinically, transdermal nicotine improves mood in smokers and a placebo-controlled pilot trial in nonsmoking adults found that transdermal nicotine significantly improved mood. As observed in smokers, nicotine's effect to increase cognitive control network activity while reducing default mode network activity will reduce depression's characteristic bias to negatively valenced stimuli and decrease rumination. Supporting this theory, nicotinic receptor activity stimulates serotonin release and protects against worsening mood with tryptophan depletion.
The Depressed Mind 2 Study examines whether enhancement of CCN function by nicotinic acetylcholine receptor agonists will improve mood and cognitive symptoms in LLD. This is supported by pilot data demonstrating that open-label administration of transdermal nicotine (TDN) patches safely improved depression severity. The investigators also observed trends suggesting that TDN may provide benefit for cognitive performance, specifically in domains of episodic memory, working memory, and attention. In other pilot data using an emotional Stroop task, TDN reduces the differences in functional magnetic resonance imaging (fMRI) activation in the cognitive control network (CCN) between Stroop conditions. Importantly, this activation change was associated with a corresponding reduction in depression severity. Based on these data, investigators hypothesize that nicotinic receptor agonists enhance CCN function in LLD and in turn this may improve depressive symptoms.
Thirty-six participants will be enrolled to test for target engagement, defined as TDN exposure dependent effect in CCN activation. Based on pilot data, the study will test for enhancement of CCN function by examining the Stroop fMRI response, or the reduction in CCN activation between incongruent and congruent conditions of the emotional Stroop task during fMRI. Investigators will assess the effects of variability in nicotine exposure on target engagement by measuring nicotine blood levels in conjunction with repeat MRI.
Primary aim: To test CCN engagement over 12 weeks of Open labeled Transdermal Nicotine(TDN).
Hypothesis1A(Target Engagement): TDN will enhance CCN function, measured as a reduction in the middle or superior frontal gyri (M/SFG) Stroop functional MRI response (the activation difference between incongruent and congruent conditions of the emotional Stroop task). 60% or more of subjects will exhibit a M/SFG z-score reduction of 0.5 or greater.
Hypothesis1B (Exposure): Higher nicotine exposure measured by patch dose or nicotine metabolite levels will be associated with a greater reduction in the M/SFG Stroop fMRI response.
