SYNCED - SYNChronized Eating in Bipolar Depression Study

Bipolar disorders (BD) are a group of complex disorders that impact mood, behaviour and cognition and are known to cause significant suffering and impairment. Circadian rhythm (your internal day/night "clock") disruption, which can involve changes in sleep-wake cycles, frequently occurs in BD. Both depression and mania are accompanied by circadian disruption. These disruptions are hypothesized to lead to mood worsening, metabolic dysfunction and inflammation. If circadian dysfunction plays a significant role in the symptoms and trajectory of BD, then treatment approaches that target these functions may lead to better outcomes. One such approach is dietary interventions. Time restricted eating (TRE) is a dietary tool that restricts the eating to an 8-12 hour window, without changing diet quality or caloric intake. Studies involving time restricted eating have been done in other conditions with promising results. There have been no studies done for mood disorders in general or bipolar disorder specifically. In this proposal, the investigators will assess two dietary interventions (TRE and nutritional counselling) to examine how TRE may represent a safe and viable adjunct to traditional treatments. The investigators aim to compare TRE with nutritional counselling, while all participants continue to receive usual care. Participants will receive support from a registered dietician and will be instructed on dietary habits. Half of participants will receive nutritional counselling and half will be asked to do TRE. Those in the TRE group will be asked to select a 10-hour window to consume all food and non-water beverages for the 8-week period. Participants will be asked to complete a screening visit to determine eligibility, and then will complete questionnaires at baseline, week 4 and week 8 examining symptoms of their illness and cognition. Participants will also provide a blood sample at baseline and week 8 for standard biochemistry tests, pregnancy testing (if applicable), and to examine inflammatory markers. Participants will also wear an actigraphy watch which provides wireless continuous monitoring of movements and ambient light. The primary outcome is feasibility and acceptability (do people agree to participate, complete the study, and follow the intervention; what do they think of the intervention). Secondary outcomes include changes in depression, anxiety, sleep, and cognition. Exploratory outcomes include inflammatory markers and circadian disruption.