Van de Vliert is to be commended for revealing and explicating the importance of climato-economic habitats on patterns of human stress. This commentary presents further arguments to suggest that climate, diet, lifestyle, and environmental settings are also able to modulate mental health. Our alternative explanation builds on prior clinical practice of climatotherapy and recent researches demonstrating that climatotherapy might be a therapeutic avenue for the sustainable development of mental health.

When taking care of a goldfish, we take into consideration water quality and oxygenation, temperature and luminosity of the aquarium, diet, and so forth. When it comes to taking care of ourselves, the impact of these environmental factors on our behaviours and mental health is often less evident.

Long before the development of theories linking the economy to climate, however, theories have involved climate as a factor in the regulation of emotions. Under the term climato-therapy, the influence of climate was described as a causal factor in mental disorders. Its action could be direct, either brutal (acute delirium linked to sun stroke) or insidious (depressive state of a more or less long duration). Its action could also be indirect, either through specific infectious diseases in countries and climates (malarial psychosis, dysenterial psychosis, etc.), or through toxic habits (opium addiction, colonial alcoholism, etc.), or finally through moral and social conditions in which they are found (nostalgia, disorientation, etc.). Admittedly, Van de Vliert discusses patterns of prevalence of mental health problems according to threat, comfort, or challenge appraisals as a competing explanation. However, for Van de Vliert climate is perceived as an element of fate and not a therapeutic tool applicable in mental health.

Surprisingly, the concept of climatotherapy, formerly used in mental health, has been taken up again primarily with regards to dermatologic disorders, such as psoriasis, atopic dermatitis (Adler-Cohen et al. Reference Adler-Cohen, Czarnowicki, Dreiher, Ruzicka, Ingber and Harari2012) or vitiligo (Czarnowicki et al. Reference Czarnowicki, Harari, Ruzicka and Ingber2011). Depending on the disorder, the described effects can either be acute or chronic (Schuh & Nowak Reference Schuh and Nowak2011).

Several hypotheses could review the first intuitions of mental treatments. First is the hypothesis that there is a link between depression and vitamin D (of which a deficiency is more important in less sunny climates), which rests on the observation that vitamin D improves depression and other mental disorders (Penckofer et al. Reference Penckofer, Kouba, Byrn and Estwing Ferrans2010), that it increases following climatotherapy, and that it reduces musculoskeletal pain, such as that encountered in fibromyalgia (Harari et al. Reference Harari, Dramsdahl, Shany, Baumfeld, Ingber and Novack2011). A second hypothesis is that mental disorders are linked to diet (Desseilles et al. Reference Desseilles, Mikolajczak and Desseilles2013), for example, the concentration of lithium in the groundwater influencing the prevalence of mood disorders (Schrauzer & Shrestha Reference Schrauzer and Shrestha1990). Third is the hypothesis linking lifestyle to mental disorders, such as the notion of the urban environment posing a mental health risk. Indeed, anxiety and mood disorders, as well as schizophrenia, are more prevalent among city dwellers (Krabbendam & van Os Reference Krabbendam and van Os2005; Mortensen et al. Reference Mortensen, Pedersen, Westergaard, Wohlfahrt, Ewald and Mors1999; Pedersen & Mortensen Reference Pedersen and Mortensen2001; Peen et al. Reference Peen, Schoevers, Beekman and Dekker2010; van Os et al. Reference van Os, Pedersen and Mortensen2004). Living in a city has also been associated with increased activity of the amygdala, known for its role in emotion regulation (Lederbogen et al. Reference Lederbogen, Kirsch, Haddad, Streit, Tost and Schuch2011; Mikolajczak & Desseilles Reference Mikolajczak and Desseilles2012).

We could also easily imagine that architecture (e.g., Roessler Reference Roessler2012) and the living environment have a psychological impact on individuals and that climate, topography, or both could influence mental health through their previous impact on what and how individuals have built and planned their surroundings. These ideas have led to the notion of environmental psychology (De Young Reference De Young, Alexander and Fairbridge1999) and to that of sustainable development, which has been popularised by the report from the World Commission on Environment and Development, created in 1983 by the United Nations. The report aims to reconcile the economic, social, and ecological dimensions of human societies. Indeed, historical sites, representations, and objects that have a cultural, scientific, symbolic, spiritual, or religious value are important manifestations of the culture, identity, and religious beliefs of a society, and they are also important factors to stability and humanity within society (United Nations 1997). Therefore, historical sites and monuments could be used as remedies to psychological imbalance caused by the rapid urbanisation of society (Council of Europe Parliamentary Assembly 1970).

Furthermore, convalescence and treatment settings – prized for their environmental or natural qualities (natural sources, thermal cures, sunbathing,…) and their services (lodging, dietary, distractions), – combined to cures of hydrotherapy, act through mental and physical rest, through the interruption of activities and professional preoccupations, and through disorientation or a change of scenery. These hydro-climatic cures were one of the first physical treatments of mental disorders.

Of course, we can isolate a lot of climatic factors, which are actually studied scientifically in dedicated protocols enabling us to shed light on their physiopathological and psychopathological implications. Let us therefore note the studies linking ambient temperature to the physiopathology of depression (Rosenthal & Vogel Reference Rosenthal and Vogel1994), or dehydration to mood (Armstrong et al. Reference Armstrong, Ganio, Casa, Lee, McDermott and Klau2012), or light to mood (Golden et al. Reference Golden, Gaynes, Ekstrom, Hamer, Jacobsen and Suppes2005), as well as high altitude and hypoxic condition to mood and cognition (de Aquino Lemos et al. Reference de Aquino Lemos, Antunes, dos Santos, Lira, Tufik and de Mello2012). Among bipolar patients, meteorological factors such as temperature could influence the onset of new episodes (Christensen et al. Reference Christensen, Larsen, Gjerris, Peacock, Jacobi and Hassenbalch2008).

Last but not least, Van de Vliert's climato-economic theory also points to the effect of global warming, but without contemplating its opportunities, consequences, or risks on mental health. Indeed, climate and its catastrophic variations can also lead to numerous psychological damages, particularly among vulnerable persons (Neria & Shultz Reference Neria and Shultz2012). The challenge in mental health comes from the fact that interventions bear on unforeseeable elements – their occurrence, extent, and consequences. These dramatic consequences to climates could become more frequent and virulent as a result of global climate change (Aldy & Stavins Reference Aldy and Stavins2012). In this way, early identification of exposed persons and a rapid and efficient intervention for individuals at risk of developing mental health disorders seem vital, alongside the consideration of climatic refugees or eco-refugees (Myers Reference Myers1994). Climate modifications can therefore be an occasion to promote mental health (Berry Reference Berry2009) adapted to specific environments, populations, and available budgets.