OK, so it s a mood disorder and a serious mental illness. It has a strong genetic component, but appears to be triggered environmentally. There are no diagnostic tests for it, just psychiatric evaluation. Most sufferers are not diagnosed until middle age, and it takes an average of around 8-10 years to get a correct diagnosis. Historically, figures suggested it affects about 0.8% of the population at some point, which makes it about half as common as schizophrenia. In recent years, bipolar disorder has become an in diagnosis, and many more people are being diagnosed at younger and younger ages. As with ADHD, this fad may well pass with time, although for the moment many celebrities appear to be popularising it. It is characterised by episodes of severe clinical depression and mania or hypomania (for definitions of those, see here: http://en.wikipedia.org/wiki/Current_diagnostic_criteria_for_bipolar_disorder ). The extreme end of mania often turns into psychosis, complete with hallucinations and delusions. During manic phases, the person s judgement and perception of reality is severely compromised, leading to risky actions with potentially damaging consequences (financially, sexually and relationship-wise). Untreated, episodes generally worsen over time due to an effect known as kindling. Untreated Bipolar sufferers are at a very high risk of suicide: 20-25% attempt it, and 15% succeed. The cycles in bipolar disorder are much longer than people generally believe. Anyone whose mood changes from minute to minute is very unlikely to be bipolar. Bipolar 1 is characterised by mood episodes lasting many months, while Bipolar 2 has episodes in the region of weeks to months. Rapid and ultra-rapid cycling bipolar disorder is rare, and cycles last days to weeks. There are many drugs available to treat the symptoms of bipolar (there is no cure). These are either anti-convulsants or anti-psychotics (personally I take both), and the most well known of these is Lithium. These drugs are heavy duty psychiatric medications and are not to be taken lightly, and most if not all of them have a range of side effects including lethargy, photosensitivity, cognitive impairment (dumb as a box of rocks), weight gain, hormone problems, hair loss and blood problems. These side effects have to be weighed against the benefits of mood stabilisation. Most patients will go through a number of different drugs before finding one that works for them.