Lansdowne et al., 1998 [95] Australia; 44 healthy students; 18 to 43 years old Test the efficiency of vitamin D supplementation on participants’ mood during winter No measurement The Positive and Negative Affect Schedule (PANAS) was used as a self-report measure of positive affectivity (PA) and negative affectivity (NA) Subjects were given 400 IU, 800 IU, or no vitamin D3 for five days during late winter in a random double-blind study None Both doses (400 IU and 800 IU) increased their reported PA by almost a full standard deviation above their population mean. NA did not decrease significantly for either dose group compared to the placebo. Even though it did not reach significance, the trend for NA was a decrease in both dose groups.

The placebo group remained practically matched the population means.

Hoogendijk et al., 2008 [94] The Netherlands; 1282 residents; 65 to 95 years old Explore if there is an association between altered calcidiol and parathyroid hormone (PTH) levels and depression Serum calcidiol concentration was determined using a competitive binding protein assay (Nichols Institute Diagnostics Inc, San Juan Capistrano, California) Depression was measured using self-reports (Centre for Epidemiologic Studies–Depression scale) and diagnostic interviews (Diagnostic Interview Schedule) None Potentially confounding factors and explanatory factors were also measured Compared to 1087 control individuals, calcidiol levels were 14% lower in 169 persons with minor depression, whereas their PTH was 5% higher. Twenty-six persons with MDD also had a lower calcidiol level by 14% and higher PTH by 33%. Decreased serum calcidiol levels and increased serum PTH levels were significantly associated with depression severity (Center for Epidemiologic Studies Depression Scale).

Jorde et al., 2008 [96] Norway; 441 subjects (BMI 28–47 kg/m); 21–70 years old Serum calcidiol was determined by immunometric (electrochemiluminescence) using an automated clinical chemistry analyzer (Modular E170; Roche Diagnostics®) Depressed mood was judged with the Beck Depression Inventory (BDI) at inclusion and the end of the study 20,000 or 40,000 IU vitamin D per week or placebo for one year in a random double-blind study Blood samples were drawn for analysis of serum calcium, creatinine, and parathyroid hormone (PTH) Patients with < 40 nmol L(-1) calcidiol levels had significantly more depressive traits as measured by the total and subscales of the BDI than patients with serum levels ≥ 40 nmol L(-1) calcidiol levels. The BDI scores improved significantly after one year in both groups with vitamin D supplementation but not in the placebo group.

Kaviani et al.,

2020 [23] Iran; 56

subjects with

mild to moderate depression and no other psychiatric disorder; 18–60 years old Assess the effects of

vitamin D supplementation on consequent serum calcidiol, depression severity, and serotonin and oxytocin in patients with mild to moderate depression The enzyme immunoassay (EIA) method was employed for assessing serum calcidiol (Euroimmun EIA kit, Lubeck, Germany) Structural clinical diagnostic interview based on the DSM–IV criteria and Beck Depression Inventory-II (BDI-II) score 50,000 IU cholecalciferol/2 weeks and control (placebo) in an 8-week double-blind, randomized clinical trial Intact parathormone (iPTH), serum

oxytocin, and

platelet serotonin After eight weeks, significant changes in the calcidiol concentrations and BDI-II scores were observed in the intervention group compared to the controls.

Differences between groups were not significant for oxytocin and serotonin, but oxytocin concentrations were significantly reduced in controls, and platelet serotonin increased more in controls.