section_path: Mental health
section_name: Mental health
paragraph_text: Mental health
  
  The recognition and understanding of mental health conditions have changed over time and across cultures and there are still variations in definition, assessment, and classification, although standard guideline criteria are widely used. In many cases, there appears to be a continuum between mental health and mental illness, making diagnosis complex. According to the World Health Organization, over a third of people in most countries report problems at some time in their life which meet the criteria for diagnosis of one or more of the common types of mental disorder. Corey M Keyes has created a two continua model of mental illness and health which holds that both are related, but distinct dimensions: one continuum indicates the presence or absence of mental health, the other the presence or absence of mental illness. For example, people with optimal mental health can also have a mental illness, and people who have no mental illness can also have poor mental health.