A significant minority of depressed patients have unrecognised bipolar disorder, a primary care study from Wales has found. Dr PhilipBland comments on the study: 'There are a number of reasons why bipolar disorder is often not recognised. Patients may perceive hypomania as normal wellbeing, distinction from personality disorder (particularly borderline personality disorder) can be difficult, and comorbid substance misuse may be misdiagnosed as the primary disorder. At the same time, early recognition is important. There are concerns that antidepressant monotherapy may be harmful in bipolar disorder, with a risk of mood destabilisation, rapid cycling and treatment resistance. Therefore, we should raise our awareness of bipolar disorder, particularly among those with early-onset, severe or treatment-resistant depression. However, I would argue against the routine use of screening questionnaires as this is likely to replace the problem of underdiagnosis with that of overdiagnosis.'