Early symptom response to antipsychotic medication as a marker of subsequent symptom change: an eighteen-month follow-up study of recent episode schizophrenia.
Differences between early- and delayed-responders to antipsychotic medication as a marker of subsequent symptom change to 18months are unknown.To examine the association between initial non-, early- and delayed-response and subsequent symptom change up to 18months in the antipsychotic treatment of the symptoms of recent-episode schizophrenia.Participants were from a double-blind randomized clinical trial of recent episode schizophrenia (n=263). Based on attainment of a 20% PANSS total change in the initial four weeks, the following groups were created and compared: "non-" (i.e., no-response): "early-" (i.e. within 2weeks) and "delayed-" (i.e. 3-4weeks) responders. Mixed modeling was used to predict PANSS percent change with group, time and the time-group interaction.Analysis of the PANSS total percent change showed significant (p<.01) group, time, and time-group interaction effects. Compared to non-responders, early-responders maintained significantly greater total response from week 5 to 44, and delayed-responders from week 5 to 20. After this time, non-responders and the other groups did not significantly differ on change. Generally, differences between the delayed- and early-responders were not statistically significance. Results were similar on the PANSS positive, negative and general psychopathology symptom subscales.Early-response is marked by up to 39weeks of longer subsequent symptom response than non-response, and infrequently differs to delayed-response. This has implications for consideration of switching and clinical trial design.