Do reductions in ghrelin contribute towards antipsychotic-induced weight gain?

We read with interest the recent meta-analysis by Goetz and Miller (2018),which reported that circulating levels of ghrelin are significantly reduced by olanzapine treatment. This finding may shed new light on the behavioural and metabolic side-effects of olanzapine, as ghrelin is widely referred to as 'the hunger hormone', due to its well-established role in appetite regulation and satiety (Higgins et al., 2007). Somewhat paradoxically, reductions in ghrelin levels are an established risk factor for both binge-eating (Geliebter et al., 2005) and obesity (Tschöp et al., 2001). Indeed, previous research has suggested the drastic weight gain observed in with second-generation antipsychotic treatment may be mediated by increases in appetite (Mayfield et al., 2016). Supporting this, recent population-scale studies have found that individuals with psychotic disorders are not only less active than the general population (Firth et al., 2018b), but also consume substantially more total calories and obesogenic foods (i.e. sugars, carbohydrates, and saturated fats) than people with othermental disorders, even after adjusting for social deprivation and education (Firth et al., 2018a).