Impact of DSM-5 changes on the diagnosis and acute treatment of schizophrenia

To examine the consequences and validity of changes in Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 diagnostic criteria for schizophrenia, eg, omission of subtypes, using a large dataset of double-blind, randomized, placebo-controlled schizophrenia trials.

Data from 22 short-term efficacy registration trials of second generation antipsychotics for the treatment of acute psychotic episodes in patients with schizophrenia (N = 5233), submitted to the Dutch regulatory authority were analyzed. We examined whether patients in these pre-DSM-5 trials met the diagnostic criteria for schizophrenia according to DSM-5. Using linear regression, we examined differences in effect size between DSM-IV subtypes and between DSM-5 symptom dimensions.

Over 99.5% of the patients met DSM-5 diagnostic criteria for schizophrenia and no differences in effect size were found between schizophrenia subtypes (P = .65). Symptom dimensions that respond best to treatment with second generation antipsychotics were hallucinations, delusions, disorganized speech, and mania (Hedge's g -0.23 to -0.31).

Results of clinical trials in patients with pre-DSM-5 schizophrenia also apply to patients diagnosed with DSM-5 schizophrenia. Omission of the classic subtypes is justified as they are not predictive of response to treatment. The DSM-5 C-RDPSS scale adds valuable information to the categorical diagnosis of schizophrenia, which is relevant for antipsychotic response.