"Constipation and dyspepsia are disturbing gastrointestinal symptoms that are often ignored in research on physical comorbidities of schizophrenia."
"The prevalence of constipation was 31.3%, and of dyspepsia 23.6%."
So said the findings reported by Tomi Virtanen and colleagues  who assessed "dyspepsia and constipation in a sample of outpatients with schizophrenia spectrum psychoses." Alongside the general practitioner assessment of such functional bowel complaints, researchers also "assessed the possible contribution of several sociodemographic, lifestyle, and clinical variables" including gender/sex and medication use.
As per the sentence above, functional bowel issues such as constipation and dyspepsia might not be unstrange bedfellows alongside a diagnosis of schizophrenia spectrum disorders. There were however some important potential 'correlates' associated with such bowel issues, not least that certain types of medication might exert some effect(s). So for example: "Clozapine use markedly increases the risk of constipation and may lead to life-threatening complications." Even something like the (not-so) humble medicine called paracetamol might also show some relationship to bowel symptoms according to the Virtanen data.
Glancing through the other peer-reviewed literature on the topic of bowel issue prevalence and schizophrenia, I was struck by how little there seems to be at present. Yes, there are various papers talking about the comorbidity of certain bowel diseases and schizophrenia  but when it comes to the question of 'how prevalent are functional bowel disorders (i.e. constipation, diarrhoea, etc) in cases of schizophrenia?' there appears to be something of a bit of a research gap. This is perhaps a more important topic than many might realise given the suggestion that 'the gut might matter' when it comes to at least some schizophrenia . Yet another example of the gut-brain axis at work eh?
The very important effect that something like medication might have on the presentation of bowel issues in schizophrenia is not to be sniffed at either. When words like: "Constipation associated with antipsychotic treatment is frequent in patients with schizophrenia. It can be severe when early detection fails." one really would think that a lot more would be done to further quantify such risk and importantly, start providing viable options to reduce any risk from such potentially severe functional bowel effects. On this matter, and minus any charges of me providing clinical and/or medical advice (I'm not), I might draw your attention to the data suggesting that the use of probiotics in cases of schizophrenia with bowel issues  (see here for further discussion) might be something to look further at. More so if one assumes that such something like constipation might be more readily described in terms of irritable bowel syndrome (IBS) for some, and the growing moves towards using probiotics as an intervention aid with that label in mind (see here). Dietary advice could also be something that could be utilised a lot more assuming that a diagnosis of schizophrenia (spectrum disorder) might confer some enhanced risk for a poor diet and nutrition .
Who knows, treating such bowel issues as and when they present might also have some interesting knock-on effects for other areas of functioning too...
 Virtanen T. et al. Dyspepsia and constipation in patients with schizophrenia spectrum disorders. Nord J Psychiatry. 2016 Aug 26:1-7.
 Mäkikyrö T. et al. Comorbidity of hospital-treated psychiatric and physical disorders with special reference to schizophrenia: a 28 year follow-up of the 1966 northern Finland general population birth cohort. Public Health. 1998 Jul;112(4):221-8.
 Severance EG. et al. Gastroenterology issues in schizophrenia: why the gut matters. Curr Psychiatry Rep. 2015 May;17(5):27.
 Dickerson FB. et al. Effect of probiotic supplementation on schizophrenia symptoms and association with gastrointestinal functioning: a randomized, placebo-controlled trial. Prim Care Companion CNS Disord. 2014;16(1). pii: PCC.13m01579.
 Teasdale SB. et al. A nutrition intervention is effective in improving dietary components linked to cardiometabolic risk in youth with first-episode psychosis. Br J Nutr. 2016 Jun;115(11):1987-93.
Virtanen T, Eskelinen S, Sailas E, & Suvisaari J (2016). Dyspepsia and constipation in patients with schizophrenia spectrum disorders. Nordic journal of psychiatry, 1-7 PMID: 27564411