Causes of Mental Disorders - Individual Characteristics

Individual Characteristics

Mental characteristics of individuals, as assessed by both neurological and psychological studies, have been linked to the development and maintenance of mental disorders. This includes cognitive or neurocognitive factors, such as the way a person perceives, thinks or feels about certain things; or an individual's overall personality, temperament or coping style or the extent of protective factors or "positive illusions" such as optimism, personal control and a sense of meaning.

Abnormal levels of dopamine activity have been implicated in a number of disorders (e.g., reduced in ADHD, increased in schizophrenia), thought to be part of the complex encoding of the importance of events in the external world. Dysfunction in serotonin and other monoamine neurotransmitters such as norepinephrine and dopamine has also been centrally implicated in mental disorders, including major depression as well as obsessive compulsive disorder, phobias, posttraumatic stress disorder, and generalized anxiety disorder, although the limitations of a simple "monoamine hypothesis" have been highlighted and studies of depleted levels of monoamine neurotransmitters have tended to indicate no simple or directly causal relation with mood or major depression, although features of these pathways may form trait vulnerabilities to depression. Dysfunction of the central gamma-aminobutyric (GABA) system following stress has also been associated with anxiety spectrum disorders and there is now a body of clinical and preclinical literature also indicating an overlapping role in mood disorder.

Findings have indicated abnormal functioning of brainstem structures in disorders such as schizophrenia, related to impairments in maintaining sustained attention. Some abnormalities in the average size or shape of some regions of the brain have been found in some disorders, reflecting genes and/or experience. Studies of schizophrenia have tended to find enlarged ventricles and sometimes reduced volume of the cerebrum and hippocampus, while studies of (psychotic) bipolar disorder have sometimes found increased amygdala volume. Findings differ over whether volumetric abnormalities are risk factors or are only found alongside the course of mental health problems, possibly reflecting neurocognitive or emotional stress processes and/or medication use or substance use. Some studies have also found reduced hippocampal volumes in major depression, possibly worsening with time depressed.