Bipolar disorder (BD) is a complex and often debilitating mental health condition characterized by marked fluctuations in mood and energy.1 People with BD tend to swing from depression to mania; manic episodes can include grandiose thinking, rapid speech, reduced need for sleep, impulsivity and risk taking, and possibly psychosis.1,2 BD is associated with impairments in functioning and cognition and a high risk of suicide.1,3-8 Individuals’ symptoms vary widely and subtypes of the disorder reflect differences in the severity of mania; bipolar I includes mania and often greater functional impairment, while bipolar II features milder, hypomanic episodes.2 BD affects about 4.4% of US adults in their lifetimes.3 The average age of onset is 25 years; BD begins most commonly in the adolescent or young adult years, but some individuals have onset later in adulthood.1,2,8,9
BD tends to co-occur with other mental health conditions and chronic physical illnesses. Common mental health comorbidities include anxiety, ADHD, PTSD, eating disorders, and substance use disorders.1,5,7,8,10 Common physical conditions include CVD, metabolic syndrome, type 2 diabetes, obesity, irritable bowel syndrome, neurological diseases, and respiratory diseases.2,5,6,8,10-12 Suicide and chronic physical comorbidities, particularly CVD, contribute to the significantly—about 20% to 30%—lower life expectancy of individuals with BD, compared with the general population.2,5,8,10-12
Etiology and Treatments
The etiology of BD is not clear, but recent research has uncovered potential genetic, epigenetic, and environmental contributors.1,2,4,8 Researchers have suggested that an interplay between oxidative stress, mitochondrial dysfunction, inflammation, and immune dysfunction may underlie the disorder.13,14 Elevated oxidative stress levels can damage cells, DNA, and mitochondria, and may contribute to immune and neurocognitive dysfunction in BD, including altered levels of neurotransmitters that affect mood.2,7,13 Mitochondrial disturbances, in turn, can increase oxidative stress and alter intracellular calcium levels, which are typically elevated in BD.2,13-15 Individuals with BD tend to have increased inflammatory markers, which can indicate high levels of inflammation systemically and neurologically.4,7,10,16,17 Additionally, some studies have found imbalances in the microbiota of people with BD, which can contribute to inflammation, oxidative stress, and immune dysfunction.2,7,14 Chronic inflammation and oxidative stress likely factor into the higher rates of chronic physical conditions in individuals with BD, including metabolic disorder, diabetes, and CVD.11,12,16
