|Classification and external resources| Eight women representing
prominent mental diagnoses in the 19th century. (Armand Gautier)
A mental disorder or psychiatric disorder is a psychological
pattern or anomaly, potentially reflected in behavior, that is
generally associated with distress or disability, and which is
not considered part of normal development in a person's culture.
Mental disorders are generally defined by a combination of how a
person feels, acts, thinks or perceives. This may be associated
with particular regions or functions of the brain or rest of the
nervous system, often in a social context. 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
Organisation (WHO), over