Background: The diagnostic stability of the ICD-10 diagnosis of mania/bipolar disorder has not been investigated in clinical practice.
Methods: All patients who got a diagnosis of mania/bipolar disorder at least once in a period from 1994 to 2002 at outpatient treatment or at discharge from psychiatric hospitalisation in Denmark were identified in a nationwide register.
Results: Totally, 4116 patients got a diagnosis of mania/bipolar disorder at least once; among these, 2315 patients (56.2%) got the diagnosis at the first contact, whereas the remaining patients (43.8%) got the diagnosis at later contacts. Approximately 30% of patients with an initial diagnosis of mania/bipolar disorder eventually changed diagnosis during follow-up. A substantial proportion of patients initially presented with prodromal syndromes such as transient psychosis, reaction to stress/adjustment disorder or mental and behavioural disorder due to psychoactive substance use and got a diagnosis of bipolar disorder later on. Especially younger but also female patients were at increased risk of delay of the diagnosis of bipolar disorder.
Limitations: Only patients from psychiatric settings were included.
Conclusions: Clinicians should, especially in younger and female patients, be more observant on manic symptoms in patients who as first glance presents with transient psychosis, reaction to stress/adjustment disorder or with psychoactive substance abuse and follow these patients more closely over time identifying putable hypomanic and manic symptoms as early as possible.