Diagnosing Bipolar Disorder A crucial step in diagnosing bipolar disorder is to rule out other possible causes of extreme mood swings. These may include brain infection or other neurological disorders, substance abuse, thyroid problem, HIV, ADHD, side effects of certain medications, or other psychiatric disorders. There is no lab test for bipolar disorder. A psychiatrist usually makes the diagnosis based on a careful history and evaluation of the patient's mood and other symptoms.
The Mood Disorder Questionnaire (MDQ) is a screening tool to check if you have Bipolar Disorder. MDQ can be administered either by a medical professional or...more at http://www.beliefnet.com/columnists/depressionhelp/2016/03/mood-disorder-questionnaire-mdq-for-bipolar-disorder.html
Also, for each ‘type’ of depression, differing ‘mixtures of causes’ have differential relevance. So, for psychotic or melancholic depression physical and biological factors are generally more relevant. By contrast, for non-melancholic depression, the role of personality (osteoporosis) and life-event stressors (accident) are generally far more relevant.