We would like to thank Prof. Hedayati for the interest shown in our systematic review and the important issues raised in his letter.

It is fair to say that we completely agree with Prof. Hedayati about the complex interplay between contextual factors and the dispositional nature of loneliness. Substantial scientific research on the interaction of contextual and dispositional variables should be taken carefully into consideration as creating protocols for interventions that might reduce loneliness in older adults. In a translational view, detailed information on the causes of loneliness could help to find out what kind of intervention is more appropriate to a specific population group.

As stated in a review on longitudinal risk factors for loneliness (Dahlberg et al., Reference Dahlberg, McKee, Frank and Naseer2022), interventions to reduce loneliness should be based on firm evidence regarding risk factors in that specific population. As mentioned by Prof. Hedayati and as confirmed in literature, the nature of loneliness is a complex matter. Dahlberg et al. (Reference Dahlberg, McKee, Frank and Naseer2022) grouped the risk factors in five main categories: (1) demographic (e.g. age, gender, ethnicity); (2) socioeconomic (e.g. education, employment status, financial situation); (3) social (e.g. partner status, relationships, social support); (4) health-related (e.g. self-perceived health, cognitive functioning, functional limitations); (5) psychological (e.g. depression, anxiety, personality). Despite the wide range of examined factors, strong evidence for a longitudinal association with loneliness was found for few considered variables. Investigated risk factors that stand out are: not being married/partnered and partner loss, a limited social network, a low level of social activity, a poor self-perceived health, and depression/depressive mood and an increase in depression.

People’s disposition towards loneliness could play an important role. The five factor model of personality (Costa and McCrae, Reference Costa and McCrae2008) has been investigated, resulting in some contradictory outcomes. Researchers in the mentioned study (Abdellaoui et al., Reference Abdellaoui2019) stated that loneliness was associated to neuroticism, whereas other studies (Cacioppo et al., Reference Cacioppo, Hawkley and Thisted2010) failed to find this association. Another study found that neuroticism increased the risk of emotional, but not social loneliness (Margelisch et al., Reference Margelisch, Schneewind, Violette and Perrig-Chiello2017). Though Abdellaoui et al. (Reference Abdellaoui2019) found that the relationship between loneliness and personality is largely explained by its relationship with neuroticism, no causal relationship could be stated, concluding that there could be some third underlying factor that influences both neuroticism and loneliness. Even the other study (Mund et al., Reference Mund, Freuding, Möbius, Horn and Neyer2020) suggests that loneliness could have trait-like features failed to find a perfect stability coefficient, leaving room for other individual and differential changes.

The comprehensible doubt Prof. Hedayati expresses about interpreting longitudinal results and interventions targeted toward loneliness without taken into account the nature of loneliness is also discussed in literature. An overview of reviews suggest that interventions tailored to the circumstances and needs of individuals, specific group or type of loneliness experienced would be more likely to result in reduction of loneliness. According to these authors, there is no one-size-fits-all approach to loneliness interventions and they recommend to assess the individual needs during the early passes of intervention, with subsequent tailoring of interventions (Victor et al., Reference Victor2018). Another scoping review of reviews that evaluated a range of interventions to combat loneliness in older people concluded that there is a need to tailor interventions to suit the needs of individuals, specific groups, or the degree of loneliness (Fakoya et al., Reference Fakoya, McCorry and Donnelly2020). In brief, future research should be aimed at discerning what interventions works from whom, in what particular context and how. Finally, given that social isolation is a prevalent long-term issue faced in the older population, interventions to reduce loneliness should have proven long-term efficacy. Though several reviews on interventions state some promising results (Fakoya et al., Reference Fakoya, McCorry and Donnelly2020; Poscia et al., Reference Poscia2018), key findings of the study of Victor and others (2018) is that evidence from the published literature for the effectiveness of interventions to alleviate loneliness is limited.

Based on these conclusions and according to literature, we agree that loneliness is a complex phenomenon and that there are many factors co-variating on individual, psychosocial, and physical level and that there is a need for further research to examine what kind of interventions might be more appropriate to a specific population, considering all possible risk factors in this particular age group, without excluding the more individual, psychological, and relational aspects.

Loneliness is associated with worse mental health and inversely with positive psychological states/traits (Lee et al., Reference Lee2019) and has a detrimental longitudinal effect on depressive symptoms. So, to our opinion, there is an urgent need for specific evidence-based interventions to reduce loneliness.