Early investigation of the mental health impacts for climate change began in the 20th century, and became more topical in the 21st. In Asia, investigations intensified markedly after the 2004 Indian Ocean earthquake and Tsunami. According to a 2011 American Psychologist review, Clayton and Doherty found that global climate change will have substantial negative impacts on mental health and wellbeing, especially for vulnerable populations and those with pre-existing serious mental illness. Research done by Berry, Bowen, and Kjellstrom in 2008 found that climate change exposes populations to trauma, which negatively impacts mental health in very serious ways. Both the Clayton study and the Berry study identify three classes of psychological impacts from global climate change: direct, indirect, and psychosocial. The Clayton study claims that in order to appreciate these impacts on psychological wellbeing, one must recognise the different cultural narratives associated with climate change, as well as how climate change and global phenomena like increased population, are interrelated. Climate change does not impact everyone equally; those of lower economic and social status are at greater risk and experience more devastating impacts. A 2018 study of CDC data connected temperature rise to increased numbers of suicides. The study revealed that hotter days could increase suicide rates and could cause approximately 26,000 more suicides in the U.S. by 2050.
“Climate change does not impact everyone equally; those of lower economic and social status are at greater risk and experience more devastating impacts.”
Climate change may also have a physiological effect on the brain, in addition to its psychological impacts. A study published in April 2020 found that by the end of the 21st century people could be exposed to avoidable indoor CO2 levels of up to 1400 ppm, triple the amount commonly experienced outdoors today. According to the authors, this may cut humans' basic decision-making ability indoors by ~25% and complex strategic thinking by ~50%.
A review of literature on natural disasters and other crises that individuals and societies navigate stated that climate change will lead to an increase in emotional responses. There is evidence that emotional responses to climate change can be adaptive if individuals have the capacity and support to reflect on and process the complexity of their emotions. This support needs to be in the form of individual, professional, societal, and legislation.