Background
Vitamin D deficiency is seen in a high proportion of people with established psychotic disorders, but it is not known if this is present at onset of the illness. We set out to examine vitamin D levels in people with their first episode of psychosis (FEP).
Method
We conducted a matched case–control study to examine vitamin D levels and rates of vitamin D deficiency in sixty nine patients presenting with their FEP and sixty nine controls matched for age, sex and ethnicity. Differences between groups were tested using student's-t tests, paired t-tests and odds ratios for further analysis.
Results
Vitamin D levels were significantly lower in cases than in controls (p < 0.001). The odds ratio of being vitamin D deficient was 2.99 in the FEP group relative to the control group. There was no correlation between vitamin D levels and length of hospitalisation in the patient group (r = − 0.027, p = 0.827).
Conclusions
We found higher rates of vitamin D deficiency in people with FEP compared to matched controls. Given that vitamin D is neuroprotective; that developmental vitamin D deficiency may be a risk factor for psychosis, and that incipient psychosis may affect lifestyle factors and diet, future studies are required to examine this association further. In the meantime, there is a need for more widespread testing of vitamin D levels in FEP and for the development of appropriate management strategies.
Low levels of vitamin D have traditionally been associated with musculoskeletal consequences (Wharton and Bishop, 2003 and Boonen et al., 2006). In recent years, however, the importance of this essential nutrient across a range of conditions has become apparent. It is increasingly recognised, for example, that low vitamin D levels are seen in cardiovascular disease (Wang et al., 2008), diabetes (Holick, 2008) and multiple sclerosis (Orton et al., 2011) (Wood, 2012) and influence the body's ability to mount immune responses (Hewison, 2011).
Vitamin D levels in the general population are higher in men than in women and decrease with increasing age (Zadshir et al., 2005). There is also a relationship between low vitamin D levels and obesity (Wortsman et al., 2000 and Vimaleswaran et al., 2013) and with smoking (Brot et al., 1999 and Cutillas-Marco et al., 2012). It has been postulated that those with increased adipose tissue stores (in which vitamin D, being fat soluble, is stored), due to obesity, have lower circulating levels of vitamin D due to this increased storage capacity (Wortsman et al., 2000). Cigarette smoking has been associated with altered vitamin D metabolism, with increased hepatic cytochrome enzyme activity (Hermann et al., 2000) suggested as the mechanism of deranged vitamin D metabolism.
In humans, skin exposure to ultraviolet B sunlight is the major primary source of vitamin D (Holick, 2004), with diet contributing a maximum of 20% (Fuller and Casparian, 2001). Vitamin D levels thus vary seasonally, with levels in late winter and early spring around half of those in the autumn reflecting ambient levels of sunlight (Hypponen and Power, 2007). People with more pigmented skin need more sunlight to produce vitamin D, so are particularly affected by limited sun exposure, with lower levels of vitamin D consistently observed in Black and Asian populations (Ford et al., 2006, Looker et al., 2008 and Mithal et al., 2009).
Vitamin D is involved in a number of brain processes including neurodevelopment, neurotransmitter expression, neurotrophic and growth factor regulation and is thought to be neuroprotective (Eyles et al., 2013). There is a growing interest in the relationship between vitamin D and mental health (Berk et al., 2008, Berg et al., 2010 and Menkes et al., 2012) and it has been proposed that developmental deficiency of vitamin D may contribute to the aetiology of schizophrenia (McGrath, 1999, McGrath et al., 2004 and McGrath et al., 2010b).
All previous reports of vitamin D deficiency in psychosis have been in those with established disorder, and therefore could be due to prolonged hospitalisation, poor nutrition, or to the prescription of anticonvulsant medications (Pack et al., 2004). To our knowledge, no data exists on vitamin D levels at first onset of the disorder. We therefore tested the hypothesis that vitamin D levels in patients with their first episode of psychosis (FEP) are lower than those in their peers in the general population.
