Bipolar disorder (BPD) is disabling, destructive and notoriously difficult to diagnose. Research indicates that up to 40% of patients diagnosed with major depressive disorder or unipolar depression actually have BPD and treating them with antidepressants alone runs an elevated risk of worsening their condition. But the issue is not one-sided: other studies found that 30% to 60% of patients diagnosed with BPD do not meet the clinical criteria for the illness and may be taking powerful mood stabilizers needlessly while failing to receive potentially beneficial therapies.