Is there a need for precision medicine in psychiatry? This was the question posed by Dr Philip Homan, University of Zurich, Switzerland at WSFBP Virtual 2021.
Precision medicine is medical care designed to optimize efficiency or therapeutic benefit for particular groups of patients, often by using genetic or molecular profiling, and is a concept that is gaining momentum in the field of psychiatry. The need for precision medicine in psychiatry (as in other fields of medicine) is based on the assumption that patients vary considerably in their response to medication.1
The average treatment effect is a reasonable assumption for individual patients
In a meta-analysis of 52 randomized controlled trials (RCTs) in adults with schizophrenia or schizoaffective diagnosis designed to evaluate whether patients vary in their response to antipsychotics, no variation was found. The authors concluded that although the study cannot rule out that subsets of patients respond differently to antipsychotics, the ‘average treatment effect’ is a reasonable assumption for individual patients.1
These findings are similar to those found for non-invasive brain stimulation. In an analysis of 130 RCTs of transcranial magnetic stimulation and transcranial direct current stimulation in patients with schizophrenia, obsessive compulsive disorder, bipolar disorder and depression, across all patients, the evidence for treatment effect variability was modest, and did not support the general assumption for the need for personalized medicine. Only for patients with schizophrenia, was some variably observed.2
Should we personalise treatment based on the adverse event profile?
We choose treatments based on adverse event profile rather than response
In terms of tolerability of antipsychotics, personalization of treatment may be more useful. In a meta-analysis evaluating variability in tolerability with antipsychotics over the past 30 years in patients with schizophrenia, there was significant variability for weight gain in the treatment group. This aligns well with clinical impressions as we know that we choose treatments based on adverse event profile rather than response, Dr Homan pointed out.3
Precision medicine in psychiatry may be useful, but defining the scope is important
Precision medicine in psychiatry may therefore be useful, but defining the scope is important. Stratification of patients into subgroups rather than individual patients may be the best way forward, with stratification according to adverse events rather than to response.