Bipolar disorders are lifelong diseases (Sadock et al., 2015). The onset of significant symptoms may occur at any age from early childhood to late in the 50s and even beyond (Sadock et al., 2015). For many, the age range between 15 and 24 seems to be when significant, disruptive swings in mood and functioning manifest clearly (Sadock et al., 2015).
Genetics is a factor in bipolar disorder, with first-degree relatives seven times more likely to experience bipolar symptoms than a person chosen from the population at random (Malectic & Raison, 2014). However, no direct "bipolar gene" has been identified. Neither race nor sex plays favorites in bipolar disorder as prevalence is distributed equally. However, certain subtypes of bipolar tend to be slightly more common in one sex or the other (APA, 2013).
Biochemistry changes in the brain accompany bipolar disorder. Several neurotransmitter systems show alteration in bipolar brain disease, making it difficult to determine what is going on exactly. Glutamate increases in the brain appear consistent in both bipolar and major depression, while poor regulation of serotonin has been associated with mania (Malectic & Raison, 2014). Hormonal imbalances, along with disruptions of the hypothalamic-pituitary-adrenal axis involved in homeostasis and the stress response, have also been implicated as biochemical contributors to the clinical picture of bipolar disorder (Malectic & Raison, 2014).
Psychodynamic factors that influence cognitive processing also play roles in bipolar disorder (Sharf, 2015). The efforts of the brain to cope with difficult to reconcile feelings of loss or acute and chronic stresses are all implicated as contributors to bipolar disorder (Sharf, 2015).