Twenty year multi-follow-up of different types of hallucinations in schizophrenia, schizoaffective disorder, bipolar disorder, and depression

Hallucinations are a salient feature of both psychotic and mood disorders. Currently there is a call for more research on the phenomenology of different forms of hallucinations, in a broader array of disorders, to further both theoretical knowledge and clinical utility. We investigated auditory, visual, and olfactory hallucinations at index hospitalization and auditory and visual hallucinations prospectively for 20 years in 150 young patients, namely 51 schizophrenia, 25 schizoaffective, 28 bipolar, and 79 unipolar depression. For the index hospitalization, the data showed schizophrenia and schizoaffective patients had a greater rate of auditory and visual hallucinations than bipolar and depression patients. However, over the longitudinal trajectory of their illness, a greater percentage of schizophrenia patients had auditory and visual hallucinations than schizoaffective patients, as well as bipolar and depression patients. Also, in contrast to the initial period, schizoaffective patients did not differentiate themselves over the follow-up period from bipolar patients. Bipolar and depression patients did not significantly differ at index hospitalization or at follow-up. We found visual hallucinations differentiated the groups to a greater degree over the 20 year course than did auditory hallucinations. These findings suggest the longitudinal course is more important for differentiating schizophrenia and schizoaffective disorder, whereas the initial years may be more useful to differentiate schizoaffective disorder from bipolar disorder. Furthermore, we found that the early presence of auditory hallucinations was associated with a reduced likelihood for a future period of recovery. No olfactory hallucinations were present at the index hospitalization in any patients. Over the course of 20 years, a minority of schizophrenia patients presented with olfactory hallucinations, and very few schizoaffective and bipolar patients presented with olfactory hallucinations. This study underscores the importance of the longitudinal course of symptoms to understand the relationship between related disorders and recovery.