Vitamin D and Health

duration varied between 8 weeks and 3-5 years. No significant effect of vitamin D supplementation
was found on post intervention depression scores. There was substantial heterogeneity between
studies (I 2 =77%). Subgroup analyses stratified by vitamin D dose, study location or sex also did not
show any effect of vitamin D supplementation.
6.324 Seasonal affective disorder (SAD) is a condition characterised by symptoms of depression, anxiety,
irritability, appetite changes, hypersomnia and fatigue that occur during winter months and abate in
the spring and summer (Rosenthal et al., 1984). Women are affected more than men and the average
age at onset is comparable to that of major depression. Some evidence suggests that incidence
increases with latitude and therefore reduced sun exposure, and phototherapy with broad spectrum
bright artificial light (>2500 lux) may improve symptoms within days in some patients. Several small
trials have failed to show any consistent beneficial effect of vitamin D supplementation in this context
(reviewed in Bertone-Johnson (2009)).
Observational studies
6.325 Cross–sectional data on serum 25(OH)D concentration and depression are inconsistent but tend to
show that patients with major or minor degrees of depression have lower serum 25(OH)D
concentration than individuals without depression (Hoogendijk et al., 2008; Ganji et al., 2010; Hoang
et al., 2011). However, depression could alter diet or behaviour in ways which would reduce serum
25(OH)D concentration.
6.326 A systematic review and meta-analysis of observational studies (Anglin et al., 2013) (10 crosssectional,
1 case-control, 3 cohort) reported that: in the case control study, lower serum 25(OH)D
concentration was found in people with depression compared with controls; in cross-sectional studies,
there was an increased OR for lowest vs highest serum 25(OH)D serum concentration (OR=1.31; 95%
CI, 1.0-1.71); the cohort studies showed a significantly increased hazard ratio of depression for the
lowest vs highest categories of serum 25(OH)D concentration (HR=2.21; 95% CI, 1.4-3.49).
Autism
6.327 It has been proposed that low serum 25(OH)D concentration in utero or in early postnatal life may be
an environmental risk factor for autism (Grant & Soles, 2009). The evidence in support of this is very
limited and is mainly ecological.
Schizophrenia
Intervention studies
6.328 No evidence is available from intervention trials in relation to vitamin D supplementation and
subsequent development of schizophrenia.
Observational studies
6.329 Epidemiological studies have reported a tendency for people with schizophrenia to be born in winter
(Kellett et al., 1978). It has been suggested that this might be related to a decrease in maternal serum
25(OH)D concentration during the winter months leading to low prenatal serum 25(OH)D
concentration which may predispose to schizophrenia (McGrath, 1999). It has been proposed that
this might explain epidemiological findings relating to schizophrenia including the impact of season of
birth, latitude gradients in incidence and prevalence, the increased risk in dark-skinned migrants to
certain countries, and the urban-rural gradient (McGrath et al., 2010a).
6.330 A large case control study in Denmark (n=848), which investigated the association between neonatal
serum 25(OH)D concentration and subsequent risk of schizophrenia, reported that both high and low
93