The Nature article this source quotes says, among other things:

However, whereas treatment with typical antipsychotics has been reported to lead to smaller volumes in certain cortical areas in subjects with schizophrenia (Dazzan et al, 2005; Lieberman et al, 2005), atypical antipsychotics might preserve cortical volume (Dazzan et al, 2005) or slow the rate of volume decreases (Lieberman et al, 2005). Thus, different antipsychotic medications might interact with the underlying disease process producing different patterns of change in cortical volume. Nevertheless, the findings of the current study at least raise the possibility that some previous reports of morphological and cellular alterations in the cerebral cortex of schizophrenia subjects might be confounded by the effects of chronic antipsychotic treatment.

Excellent post @Yaowen!