Causes of mental disorders
A mental disorder is an impairment of the mind disrupting normal thinking, feeling, mood, behavior, or social interactions, and accompanied by significant distress or dysfunction.
[6] Risk factors for mental illness include psychological trauma, adverse childhood experiences, genetic predisposition, and personality traits.
[9] Mental illnesses have risk factors, for instance including unequal parental treatment, adverse life events and drug use in depression, migration and discrimination, childhood trauma, loss or separation in families, and cannabis use in schizophrenia and psychosis, and parenting factors, child abuse, family history (e.g. of anxiety), and temperament and attitudes (e.g. pessimism) in anxiety.
This view was held well into the late 1990s, in which people still believed this child-parent relationship was a large determinant of severe mental illness, such as depression and schizophrenia.
[citation needed] A practical mixture of models will explain particular issues and disorders, although there may be difficulty defining boundaries for indistinct psychiatric syndromes.
A related view, the diathesis-stress model, posits that mental disorders result from genetic dispositions and environmental stressors, combining to cause patterns of distress or dysfunction.
Biological factors include genetics, prenatal damage, infections, exposure to toxins, brain defects or injuries, and substance abuse.
In November 1999, Biological Psychiatry published a literature review by psychiatrists Joseph Biederman and Thomas Spencer found the average heritability estimate of ADHD from twin studies to be 0.8,[30] while a subsequent family, twin, and adoption studies literature review published in Molecular Psychiatry in April 2019 by psychologists Stephen Faraone and Henrik Larsson that found an average heritability estimate of 0.74.
There are multiple gene variants which each slightly increase the likelihood of a person having ADHD; it is polygenic and thus arises through the accumulation of many genetic risks each having a very small effect.
[55][59] The largest and most recent genome-wide association study failed to find any locus that exerts a large effect, reinforcing the idea that no single gene is responsible for bipolar disorder in most cases.
The research on Lyme disease caused by a deer tick and toxins is expanding the link between bacterial infections and mental illness.
Findings on the relationship between TBI severity and prevalence of subsequent psychiatric disorders have been inconsistent, and occurrence relates to prior mental health problems.
Closed injury head trauma symptoms include; Deficits in abstract reasoning ability, judgment, memory, and marked personality changes.
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 medication use or substance use.
[citation needed] Abnormal levels of dopamine activity correspond with several disorders (reduced in ADHD and OCD, and increased in schizophrenia).
Studies of depleted levels of monoamine neurotransmitters show an association with depression and other psychiatric disorders, but "... it should be questioned whether 5-HT [serotonin] represents just one of the final and not the main, factors in the neurological chain of events underlying psychopathological symptoms...." Simplistic "chemical imbalance" explanations for mental disorders have never received empirical support; and most prominent psychiatrists, neuroscientists, and psychologists have not espoused such ill-defined, facile etiological theories.
The following 1967 quote from renowned psychiatric and neuroscience researchers exemplifies this more sophisticated understanding (in contrast to the woolly "chemical imbalance" notion).
[13] Environmental factors include but are not limited to dysfunctional home life, poor interpersonal relationships, substance abuse, not meeting social expectations, low self-esteem, and poverty.
[13] The British charity organisation Mind lists childhood abuse, trauma, violence, neglect, social isolation, discrimination, grief, stress, homelessness, social disadvantage, debt, unemployment, caring for a family member or friend, and significant trauma as an adult (such as war, an accident, or being the victim of a violent crime) as possible triggers of an episode of mental illness.
[74] Mistreatment in childhood or adulthood (including sexual-, physical-, and emotional abuse, domestic violence, and bullying) has been linked to the onset of mental disorders through an interaction of societal, familial, psychological, and biological factors.
The psychological resilience of an individual can be affected by genetics, temperamental characteristics, cognitive flexibility, coping strategies, and previous experiences.
[77] For example, in the case of bipolar disorder, stress is not a specific cause but does place genetically and biologically vulnerable people at risk for more severe forms of the illness.
[82] A child's neurological development can be disrupted when chronically exposed to stressful events, and his/her cognitive functioning and/or ability to cope with negative emotions can diminish.
[92] Early social privation, and the lack of "ongoing, harmonious, secure, committed" relationships have been implicated in the development of mental illnesses.
Divorcees may have emotional adjustment problems due to a loss of intimacy and social connections; however, new statistics show that the negative effects of divorce have been overstated.
[98] Being perceived as someone who does not "fit in" can result in bullying and other types of emotional abuse,[99][100] which can lead to the victim experiencing depression, anger, and loneliness.
Impoverished people in England, defined as those who live in the lowest 20% income bracket, are two to three times more likely to develop mental illness than those of a higher economic class.
[102] This increased risk remains consistent for all poor individuals regardless of any in-group demographic differences, as all disadvantaged families experience economic stressors such as unemployment or lack of housing.
[105] Problems in one's community or culture including poverty, unemployment or underemployment, a lack of social cohesion, and migration have been associated with the development of mental disorders.
Psychological stressors, which can trigger mental illness, are as follows: emotional, physical, or sexual abuse, loss of a significant loved one, neglect, and being unable to relate to others.
