People’s mental health and related behaviour, is positively or negatively influenced by both external social and climate factors. According to the World Health Organisation, mental health problems are set to increase significantly by the year 2020, and will be the second greatest cause of illness after heart disease by 2050 if present trends continue.

A rapid change in climate is likely to influence and increase mental health issues. This is will be especially evident in the case of climate-related natural hazards, where property losses and displacement from residences can cause significant psychological stress, with long-lasting effects on anxiety levels and depression. It is known that social disruptions resulting from family and community dislocations due to extreme weather events pose a special stress for children and those of lower socio-economic status.

For instance, many in the New Orleans medical community think that Hurricane Katrina is still killing. Health experts say that survivors of the fierce storm are dying from the effects of both psychological and physical stress. People are now dying from the dust and mould in housing, from financial problems and are deeply disturbed by fear of crime.

In a recent report, a New Orleans coroner Dr. Frank Minyard said that he had no doubt that Katrina was still killing residents. The doctor went on record to say, “People with pre-existing conditions that are made worse by the stress of living here after the storm. Old people who are just giving up. People who are killing themselves because they feel they can’t go on,”

Medical officials say deaths in New Orleans jumped from 11.3 per 1,000 deaths to 14.3 per 1,000, which is a leap of more than 25 percent. Social workers a recording a tripling of people with mental health problems, particularly in; depression, suicidal, anxiety, abuse of drugs and alcohol, and a range of physical problems.

Further studies in 2007 show that about half of adult New Orleans residents suffered from anxiety and mood disorders months after Hurricane Katrina devastated the city, a higher rate than after most natural disasters. Depression, panic disorders, and post-traumatic stress were diagnosed in 49 percent of New Orleans residents surveyed five to seven months after the storm struck on August 29, 2005, a study found.

“Given that human mental health is a state of being that is both affected by and affects the world in which we live, the link between mental health (what we think, feel, believe and ultimately do) and climate change is critical if we are to achieve positive change. Currently western ways of thinking and doing perpetuate the illusion that we are not an integral part of a planetary system, but rather above and in control of it. Human well-being – indeed survival – is likely to be very limited if this world view does not change.” (Andrew Lyon and Maddy Halliday, 2005, Climate Change and Mental Health in the 21st Century, International Futures Forum)

If we do not take urgent steps to reduce our greenhouse gas emissions, rising mental health issues will be another social cost that our society will need to bear.