Knowles and colleagues [16] examined
this question in a meta-analysis. Based on examination of articles
published between 2006 and 2009, they concluded that several
mediating factors, especially the dosage of anti-psychotic drugs, affect
the processing speed of people with schizophrenia. In comparison,
others have argued that cognitive deficits are a central component of
schizophrenia and not a secondary effect of drug therapy [17]. These
researchers claimed that cognitive deficits should be considered a
third group of symptoms of the illness, in addition to positive and
negative symptoms. Some have also contended that a cognitive
deficit can be discerned even during the first episode of the illness,
indicating that it is not a result of medication. It would be interesting
in future research to examine the effect of medication further. For
instance, the dosage of antipsychotic drugs could be transformed to
chlorpromazine equivalents, followed by an analysis of correlation
with basic learning functions