Mental health problems are more common and include the mental ill health that can be experienced temporarily as a reaction to the stresses of life. Mental health problems are less severe than mental illnesses, but may develop into a mental illness if they are not effectively dealt with. Mental illnesses cause a great deal of suffering to those experiencing them, as well as their families and friends. Furthermore, these problems appear to be increasing. According to the World Health Organization, depression will be one of the biggest health problems worldwide by the year 2020.