We thank Aymerich et al for their comments and important suggestions for future research. We agree that excessive daytime somnolence (as contrasted with total sleep duration) may have specific relevance for the motivation and pleasure (MAP) domain of symptoms in schizophrenia. There are additional difficulties in measuring daytime sleep duration, including the potential for circadian phase shift to be associated with both schizophreniaReference Walker, Walton and Nelson1 and antipsychotic medication.Reference Moon, Lavin, Storch and Linnaranta2 Our studyReference Wolpe, Chen, Kirkpatrick, Jones, Jenkins and Cardinal3 adopted the widely used approach of self-reported total sleep duration, which is readily amenable to use in routine clinical practice. However, both detailed sleep diaries and actigraphy hold promise for future research in this field.
Although patients with treatment-resistant schizophrenia (TRS) taking clozapine are an important and common subgroup of those with schizophrenia,Reference Qubad and Bittner4 we agree that it is important to study factors affecting MAP in broader groups of patients, as well as the effects of other medications and mediators. Whether the potential benefits of clozapine extend beyond those with TRS as postulated by Aymerich et al is an open question; clozapine remains underused for TRS.Reference Qubad and Bittner4 Although there are limitations when studying patients taking the same principal antipsychotic, this approach also has key advantages, as clinical and basic researchers strive to account for confounding variables such as medications, which may in fact have contrasting effects on negative symptoms.Reference Gold, Waltz and Frank5
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