Table 1 The characteristics of the included studies

De Moortel et al., 2015 [32]

European

Cross-sectional

European Social Survey (ESS); face-to-face interviews.

Male (n = 7119) and female (n = 6988) employees, aged 15–65 years; approx. 12% described as living alone (percentage stated per welfare regime).

WHO-5 Well-Being Index: three items

Good mental wellbeing (positive mental health) was less prevalent for women living alone, compared to women without children living with a partner who did half or more of the household labour (prevalence ratio among women: 0.81 (95% confidence interval 0.72–0.90) and among men: 0.98 (0.89–1.08)).

Dreger et al.,2014 [33]

European

Cross-sectional

European Quality of Life Survey (EQLS); face-to-face interviews.

Men (n = 21,066) and women (n = 22,569), aged 18 years and over; 8926 men and 10,749 women described as living alone.

WHO-5 Well-Being Index

Living alone was associated with positive mental health in both genders. Living without a partner was significantly associated with low positive mental health among both genders (odds ratio among men: 1.18 (95% confidence interval 1.07–1.30) and among women: 1.17 (1.09–1.25)).

Lukaschek et al., 2017 [34]

Southern Germany

Cross-sectional

The KORA (Cooperative Health Research in the Region of Augsburg) -Age study; telephone interview or postal questionnaire.

Participants aged 65 years or older: n = 3602 (men n = 1750; women n = 1822); 335 men and 852 women described as living alone.

WHO-5 Well-Being Index

The impact of living alone on low subjective wellbeing (positive mental health) was significant only in women. Living alone increased the odds of having low subjective wellbeing in women (odds ratio: 1.43 (95% confidence interval 1.10–1.87)), but not significantly in men (1.19 (0.85–1.68)).

Oates et al., 2017 [35]

UK

Cross-sectional

UK mental health nurses (MHN); online questionnaire.

Female (n = 159) and male (n = 65) mental health nurses; living alone (n = 37, including both sexes).

Warwick-Edinburgh Mental Well-Being Scale (WEMWBS)

Household size was not significantly correlated with subjective wellbeing (positive mental health), although those living alone had lower mean subjective wellbeing measure score. Mean score of those living alone: 46.69 (standard deviation 8.30), living with 1 person: 48.88 (7.95), living with 2–3 others: 46.89 (8.54) and living with 4+ others: 47.60 (8.33).