Living alone has become more common in today’s societies. In 2017, one third (33.6%) of households in the EU (European Union) and around 40% of households in the Nordic countries (with the exception of Iceland) were single-person households [1]. The number of people living alone is likely to continue to increase globally among both older people and working adults [2].
The definitions of living alone or being single may vary. Nowadays, official marital status no longer necessary reflects an individual’s living arrangements as single, divorced, and widowed persons may live alone or with other people such as a partner, children, parents, or other unrelated persons. Thus, more than official marital status, living arrangements may better describe one’s social bonds. In addition, people living alone do not constitute a uniform group. People living alone may be at very different life stages depending on their age, gender, education, and work status. Moreover, living arrangements can change several times during an individual’s life course. In this review, living alone is understood as only one person living in a household at the time of the research, in other words, a household size of one person. As Jamieson et al. stated [2] ‘The essence of living alone is simple: nobody else lives in the same living space or routinely shares everyday domestic life’ (p. 5).
Earlier studies have produced conflicting results concerning the association between living alone and mental health. According to some studies, living alone does not constitute a risk factor to mental health [3, 4]. On the other hand, some authors have reported associations with depression, poorer experienced health and quality of life, and experiences of loneliness [5,6,7,8]. Further, research shows that people living alone face challenges that may place a potential burden on their mental wellbeing, such as financial difficulties and higher living costs as they do not have the scale advantage of those living with another adult [5, 9]. There is therefore a need to further examine the relationship between living alone and positive mental health.
The term positive mental health is often used and understood in policy and academic literature as interchangeable with the term mental wellbeing [10, 11]. Furthermore, in research, both of these concepts have sometimes been operationalised under the concept of subjective wellbeing [12,13,14]. In this review, positive mental health is understood as being interchangeable with mental wellbeing or subjective wellbeing.
Positive mental health is based on the assumption that mental health is something positive, consists of wellbeing, and is more than the absence of mental illness [15]. It is recognised as a key resource for health and wellbeing [16]. Positive mental health has been shown to be associated with mortality, physical health, social functioning, and academic achievement, as well as with mental illness [13, 17, 18]. It is currently receiving increased attention in research, policymaking, and clinical practice [19], and it has been recognised as a priority research area in public mental health [20]. Positive mental health is conceived as a multi-faceted construct that comprises both hedonic and eudaimonic elements. The hedonic perspective focuses on subjective experience of happiness and life satisfaction. The eudaimonic perspective, on the other hand, views wellbeing as something more than subjective feelings, and focuses on psychological functioning and self-realisation [11, 12]. Positive mental health includes individual resources, such as self-esteem, optimism and a sense of mastery and coherence; the ability to initiate, develop and sustain mutually satisfying personal relationships; and the ability to cope with adversities [21].
Efforts to investigate positive mental health have been hampered by a shortage of valid instruments suitable for measuring the attributes of positive mental health. The Warwick-Edinburgh Mental Well-being Scale (WEMWBS) measures positive mental health, covering both the hedonic and eudaimonic aspects of mental wellbeing. The scale consists of 14 positively worded items covering ‘positive affect (feelings of optimism, cheerfulness, relaxation), satisfying interpersonal relationships, and positive functioning (energy, clear thinking, self-acceptance, personal development, competence and autonomy)’ ([22], p. 3). The scale was developed to enable the monitoring of mental wellbeing in the general population and the evaluation of projects, programmes, and policies which aim to improve mental wellbeing. There is also a shortened version of the WEMWBS with seven items (SWEMWBS) [23]. The scale has been used in national surveys in Scotland and England [24, 25]. In the Scottish Health Survey, in the 2012 and 2013 combined dataset [24], the WEMWBS scores were lowest for adults who were separated. In the Health Survey for England, in the 2010 and 2011 combined dataset [25], people who were single, divorced, or widowed had lower wellbeing scores than those who were married or lived as a couple. Both studies described marital status and did not differentiate those who were living alone for real.
An instrument similar to the WEMWBS is the WHO-5 Well-Being Index [26]. The index shares common features with the WEMWBS measurement, capturing positive affect and wellbeing [22, 27] and measuring both the hedonic and eudaimonic aspects of wellbeing [26]. The index is a positively worded 5-item questionnaire measuring current mental wellbeing. The scale was first presented at a WHO (World Health Organization) meeting in Stockholm in 1998. Since then, the WHO-5 Well-Being Index has been validated in a number of studies with regard to both its clinical and psychometric validity [28].
Despite the high number of the population living alone, research directed specifically towards mental wellbeing issues related to living alone has been limited. The objective of this review is to collect and assess the body of empirical research on the association between living alone and positive mental health. The review concentrates on adults living alone and on two indicators that measure positive mental health, the WEMWBS and the WHO-5 Index as they both comprise the hedonic and eudaimonic aspects of mental wellbeing.