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Psychol Med. 2011 Jul;41(7):1481-8. doi: 10.1017/S0033291710002035. Epub 2010 Oct 20.

The different trajectories of antipsychotic response: antipsychotics versus placebo.

Author information

1
Institute of Psychiatry, King's College London, London, UK.

Abstract

BACKGROUND:

It is generally accepted that antipsychotics are more effective than placebo. However, it remains unclear whether antipsychotics induce a pattern or trajectory of response that is distinct from placebo. We used a data-driven technique, called growth mixture modelling (GMM), to identify the different patterns of response observed in antipsychotic trials and to determine whether drug-treated and placebo-treated subjects show similar or distinct patterns of response.

METHOD:

We examined data on 420 patients with schizophrenia treated for 6 weeks in two double-blind placebo-controlled trials using haloperidol and olanzapine. We used GMM to identify the optimal number of response trajectories; to compare the trajectories in drug-treated versus placebo-treated patients; and to determine whether the trajectories for the different dimensions (positive versus negative symptoms) were identical or different.

RESULTS:

Positive symptoms were found to respond along four distinct trajectories, with the two most common trajectories ('Partial responder' and 'Responder') accounting for 70% of the patients and seen proportionally in both drug- and placebo-treated. The most striking drug-placebo difference was in the 'Dramatic responders', seen only among the drug-treated. The response of negative symptoms was more modest and did not show such distinct trajectories.

CONCLUSIONS:

Trajectory models of response, rather than the simple responder/non-responder dichotomy, provide a better statistical account of how antipsychotics work. The 'Dramatic responders' (those showing >70% response) were seen only among the drug-treated and make a significant contribution to the overall drug-placebo difference. Identifying and studying this subset may provide specific insight into antipsychotic action.

PMID:
20961479
DOI:
[Indexed for MEDLINE]

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