How can I differentiate between borderline personality disorder and bipolar disorder in a primary care setting?

In primary care, differentiating borderline personality disorder (BPD) from bipolar disorder involves careful clinical assessment focusing on symptom patterns and history.

BPD is characterised by marked emotional instability, persistent risk-taking behaviour, and repeated self-harm, with symptoms often fluctuating rapidly within hours to days rather than distinct mood episodes lasting days to weeks or longer. Consider referral to community mental health services if these features are present, especially with repeated self-harm or emotional instability ¹.

In contrast, bipolar disorder involves distinct episodes of mania, hypomania, and depression, with mood changes typically lasting weeks and associated with episodic overactivity, disinhibition, and sustained behavioural changes. A full psychiatric assessment should document detailed mood history, episode patterns, triggers, and family history ².

Key differentiators include the temporal pattern of mood symptoms (rapid mood shifts in BPD vs. sustained mood episodes in bipolar disorder), the presence of impulsive self-harm and emotional instability in BPD, and the episodic nature of mania or hypomania in bipolar disorder ¹,².

In primary care, if BPD is suspected due to emotional instability and risk behaviours, referral to specialist personality disorder services or community mental health teams is recommended for assessment and management ¹. For suspected bipolar disorder, referral to specialist mental health services is advised to confirm diagnosis and initiate treatment ².