The NICE guidelines recommend that the diagnosis of bipolar disorder should be based on a full psychiatric assessment that documents a detailed history of mood episodes, including periods of overactivity, disinhibition, or other episodic and sustained changes in behaviour, as well as symptoms between episodes, triggers, patterns of relapse, and family history NICE CG185.
Assessment should also include evaluation of the development and changing nature of the disorder throughout the person's life, social and personal functioning, current psychosocial stressors, and potential physical and mental comorbidities NICE CG185.
It is important to consider differential diagnoses such as schizophrenia spectrum disorders, personality disorders, substance misuse, alcohol-use disorders, attention deficit hyperactivity disorder, and physical disorders like hypo- or hyperthyroidism NICE CG185.