Epidemiology and risk factors for bipolar disorder

Abstract

Bipolar disorder is a multifactorial illness with uncertain aetiology. Knowledge of potential risk factors enables clinicians to identify patients who are more likely to develop bipolar disorder, which directs further investigation, follow up and caution when prescribing. Ideally, identifying directly causative factors for bipolar disorder would enable intervention on an individual or population level to prevent the development of the illness, and improve outcomes through earlier treatment. This article reviews the epidemiology of bipolar disorder, along with putative demographic, genetic and environmental risk factors, while assessing the strength of these associations and to what extent they might be said to be 'causative'. While numerous genetic and environmental risk factors have been identified, the attributable risk of individual factors is often small, and most are not specific to bipolar disorder but are associated with several mental illnesses. Therefore, while some genetic and environmental factors have strong evidence supporting their association with bipolar disorder, fewer have sufficient evidence to establish causality. There is increasing interest in the role of specific gene-environment interactions, as well as the mechanisms by which risk factors interact to lead to bipolar disorder.

Cannabis use in early adulthood is prospectively associated with prescriptions of antipsychotics, mood stabilizers, and antidepressants

“…Our result of a robust association between cannabis use and prescription of mood stabilizers strengthens the relatively new assumption of cannabis use as a risk factor for bipolar disorder . The effect size for the association between cannabis and mood stabilizers was comparable to the effect size for association between cannabis and antipsychotics, a magnitude similar also to the effect sizes found in studies using a diagnosis of bipolar disorder as outcome .…”

“…While some studies have found that cannabis use increases the risk of first onset of manic symptoms and bipolar disorder by a factor of more than four, others have found the association to be non‐significant after adjustment for confounders . There is a growing conception that cannabis use can act as a risk factor for the onset of bipolar disorder though the causal direction is debated .…”

Tumor necrosis factor receptor 2: A potential target for antidepressant drug development

“…Mood disorders are a class of psychiatric illnesses that are defined by the presence of symptoms that severely affect mood . Major depression and bipolar disorder are two common mood disorders, affecting approximately 6% and 2.4% of the world population, respectively. Major depression is characterized by a unipolar depressive state that includes persistent low mood, anhedonia, sleep disturbances and motivational deficiencies, whereas bipolar disorder is uniquely characterized by mood swings between depression, mania and euthymia .…”

“…Major depression and bipolar disorder are two common mood disorders, affecting approximately 6% and 2.4% of the world population, respectively. Major depression is characterized by a unipolar depressive state that includes persistent low mood, anhedonia, sleep disturbances and motivational deficiencies, whereas bipolar disorder is uniquely characterized by mood swings between depression, mania and euthymia . Cytokine‐mediated inflammatory responses have now emerged as potential contributors to the pathophysiologies of mood disorders .…”

“…Major depression is characterized by a unipolar depressive state that includes persistent low mood, anhedonia, sleep disturbances and motivational deficiencies, 2 whereas bipolar disorder is uniquely characterized by mood swings between depression, mania and euthymia. 3 Cytokine-mediated inflammatory responses have now emerged as potential contributors to the pathophysiologies of mood disorders. 4 In addition, the pro-inflammatory cytokine, tumor necrosis factor (TNF) a, and its associated pathways have emerged as a promising path to target with new therapies that might be effective in treating depression.…”