Etiology of psychopathology
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. The causes of mental disorders are very complex and vary depending on the particular disorder and the individual. Although the causes of most mental disorders are not fully understood, researchers have identified a variety of biological, psychological, and environmental factors that can contribute to the development or progression of mental disorders. Most mental disorders result in a combination of several different factors rather than just a single factor.
Research results.
Risk factors for mental illness include psychological trauma, adverse childhood experiences, genetic predisposition, and personality traits. Correlations between mental disorders and substance use are also found to have a two way relationship, in that substance use can lead to the development of mental disorders and having mental disorders can lead to substance use/abuse. This effect is stronger and more reliable in some substance use than others, such as smoking.
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. Many psychiatric disorders include problems with impulse and other emotional control.
In February 2013, a study found genetic links between five major psychiatric disorders: autism, ADHD, bipolar disorder, major depressive disorder, and schizophrenia. Abnormal functioning of neurotransmitter systems is also responsible for some mental disorders, including serotonin, norepinephrine, dopamine, and glutamate system's abnormal functioning. Differences have also been found in the size or activity of specific brain regions in some cases. Psychological mechanisms have also been implicated, such as cognitive (e.g. reasoning) biases, emotional influences, personality dynamics, temperament, and coping style. Studies have indicated that variation in genes can play an important role in the evolution of mental disorders, although the reliable identification of connections between specific genes and specific disorders has proven more difficult. Environmental events surrounding pregnancy (such as maternal hypertension, preeclampsia, or infection) and birth have also been implicated. Traumatic brain injury may increase the risk of developing certain mental disorders. Throughout the years, there have been inconsistent links found to certain viral infections, substance misuse, and general physical health that have been false.
Adverse experiences affect a person's mental health, including abuse, neglect, bullying, social stress, traumatic events, and other overwhelming life experiences. The specific risks and pathways to particular disorders are less clear, however. Aspects of the wider community have also been implicated, including employment problems, socioeconomic inequality, lack of social cohesion, problems linked to migration, and features of particular societies and cultures. Mental stress is a common cause of mental illnesses, so finding a coping solution to cope with mental stress would be beneficial. Many solutions that have helped reduce stress are yoga, exercise, and some medications that may help.
Theories.
General theories.
Several theories or models seek to explain the causes (etiology) of mental disorders. These theories may differ in regards to how they explain the cause of the disorder, how to treat the disorder, and how they classify mental disorders. Theories also differ about the philosophy of mind they accept; that is, whether the mind and brain are identical or not. 
During most of the 20th century, mental illness was ascribable to problematic relationships between children and their parents. 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. In the 21st century, additional factors have been identified such as genetic contributions, though experience also plays a role. So, the perceived causes of mental illness have changed over time and will most likely continue to alter while more research develops throughout the years.
Outside the West, community approaches remain a focus.
A practical mixture of models will explain particular issues and disorders, although there may be difficulty defining boundaries for indistinct psychiatric syndromes.
Medical or biomedical model.
An overall distinction is also commonly made between a "medical model" (also known as a biomedical or disease model) and a "social model" (also known as an empowerment or recovery model) of mental disorder and disability, with the former focusing on hypothesized disease processes and symptoms, along with latter focusing on hypothesized social constructionism and social contexts.
Biological psychiatry has tended to follow a biomedical model focused on organic or "hardware" pathology of the brain, where many mental disorders are conceptualized as disorders of brain circuits shaped by a complex interplay of genetics and experience.
The social and medical models of mental disorders each work to identify and study distinct aspects, solutions, and potential therapies of disorders. The intersection and cross reference between the two models can further be used to develop more holistic models of mental disorders. Many criticisms historically of each model is the exclusivity of the other perspective. Therefore, intersectional research improved the impact and importance of future findings.
Biopsychosocial model.
The primary model of contemporary mainstream Western psychiatry is the biopsychosocial model (BPS), which integrates biological, psychological, and social factors. The Biopsychosocial model was first conceptualised by George Engel in 1977, suggesting that to understand a person's medical condition it is not simply the biological factors to consider, but also the psychological and social factors . The biopsychosocial approach systematically considers biological, psychological, and social factors and their complex interactions in understanding health, illness, and health care delivery. Biological, psychological, and social factors exist along a continuum of natural systems. The factors within the model contain the following:
This model is commonly used for case conceptualization of psychological disorders as well as chronic pain, with the view that the pain is a psychophysiological behavior pattern that cannot be categorised into biological, psychological, or social factors alone. 
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. The model is one way to explain why some individuals are more vulnerable to mental disorders than others. Additionally, it explains why some people may develop a mental disorder after exposure to stressful life events while others do not.
Psychoanalytic theories.
Psychoanalytic theories focus on unresolved internal and relational conflicts. These theories have been predicated as explanations of mental disorders. Many psychoanalytic groups are said to adhere to the biopsychosocial model and to accept an eclectic mix of subtypes of psychoanalysis. Sigmund Freud developed the psychoanalytic theory. This theory focuses on the impact of unconscious forces on human behavior. According to Freud, a personality has three parts: the id, ego, and superego. The id operates under the pleasure principle, the ego operates under the reality principle, and the superego is the "conscience" and incorporates what is and is not socially acceptable into a person's value system. According to the psychoanalytic theory, there are five stages of psychosexual development that everyone goes through the oral stage, anal stage, phallic stage, latency stage, and genital stage. Mental disorders can be caused by an individual receiving too little or too much gratification in one of the psychosexual developmental stages. When this happens, the individual is said to be in that developmental stage.
Attachment theory.
Attachment theory is a kind of evolutionary-psychological approach sometimes applied in the context of mental disorders, which focuses on the role of early caregiver-child relationships, responses to danger, and the search for a satisfying reproductive relationship in adulthood. According to this theory, a child's attachment is to a nurturing adult, the more likely that child will maintain healthy relationships with others in their life. As found by the Strange Situation experiment run by Mary Ainsworth based on the formulations of John Bowlby, there are four patterns of attachment: secure attachment, avoidant attachment, disorganized attachment, and ambivalent attachment. Later research found the fourth pattern of attachment is known as disorganized disoriented attachment. Secure attachments reflect trust in the child-caretaker relationship while insecure attachment reflects mistrust. The security of attachment in a child affects the child's emotional, cognitive, and social competence later in life.
Evolutionary psychology.
Evolutionary psychology and evolutionary psychiatry posit that mental disorders involve the dysfunctional operation of mental modules adapted to ancestral physical or social environments but not necessarily to modern ones. Behavioral abnormalities that resemble human mental illness have been found in related species (great apes).
Other theories suggest that mental illness could have evolutionary "advantages" for the species, including enhancing creativity and stress to enhance survival by activating the flight-or-fight response in anticipation of danger.
Mania and depression could have benefited from seasonal changes by helping to increase energy levels during times of plenty and rejuvenating energy during times of scarcity. In this way, mania was set in motion during the spring and summer to facilitate energy for hunting; depression worked best during the winter, similar to how bears hibernate to recover their energy levels. This may explain the connection between circadian genes and Bipolar Disorder and explain the relationship between light and seasonal affective disorder.
Biological factors.
Biological factors consist of anything physical that can cause adverse effects on a person's mental health. Biological factors include genetics, prenatal damage, infections, exposure to toxins, brain defects or injuries, and substance abuse. Many professionals believe that the cause of mental disorders is the biology of the brain and the nervous system.
"Mind" mentions genetic factors, long-term physical health conditions, and head injuries or epilepsy (affecting behavior and mood) as factors that may trigger an episode of mental illness.
Genetics.
Some rare mental disorders are caused only by genetics such as Huntington's disease.
Family linkage and some twin studies have indicated that genetic factors often play a role in the heritability of mental disorders. The reliable identification of specific genetic variation can cause indication of higher risk to particular disorders, through linkage, Genome Wide Association Scores or association studies, has proven difficult. This is due to the complexity of interactions between genes, environmental events, and early development or the need for new research strategies. No specific gene results in a complex trait disorder, but specific variations of alleles result in higher risk for a trait. The heritability of behavioral traits associated with a mental disorder may be in permissive than in restrictive environments, and susceptibility genes probably work through both "within-the-skin" (physiological) pathways and "outside-the-skin" (behavioral and social) pathways. Investigations increasingly focus on links between genes and endophenotypes because they are more specific traits. Some include neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, or neuropsychological, rather than disease categories. Concerning a well-known mental disorder, schizophrenia, it is said with certainty that alleles (forms of genes) were responsible for this disorder. Some research has indicated only multiple, rare mutations are thought to alter neurodevelopmental pathways that can ultimately contribute to schizophrenia; virtually every rare structural mutation was different in each individual.
Research has shown that many conditions are polygenic meaning there are multiple defective genes rather than only one that is responsible for a disorder, and these genes may also be pleiotropic meaning that they cause multiple disorders, not just one. Schizophrenia and Alzheimer's are both examples of hereditary mental disorders. When exonic genes encode for proteins, these proteins do not just affect one trait. The pathways that contribute to complex traits and phenotypes interact with multiple systems, even though proteins have specific functions. 
brain plasticity (neuroplasticity) raises questions of whether some brain differences may be caused by mental illnesses or by pre-existing and then causing them.
Prenatal damage.
Any damage that occurs to a fetus while still in its mother's womb is considered prenatal damage. Mental disorders can develop if the pregnant mother uses drugs or alcohol or is exposed to illnesses or infections during pregnancy. 
Environmental events surrounding pregnancy and birth have increased the development of mental illness in the offspring. Some events may include maternal exposure to stress or trauma, conditions of famine, obstetric birth complications, infections, and gestational exposure to alcohol or cocaine. These factors have been hypothesized to affect areas of neurodevelopment, general development, and restrict neuroplasticity.
Infection, disease and toxins.
Infection.
There have been some findings of links between infection by the parasite Toxoplasma gondii and schizophrenia.
AIDS has been linked to some mental disorders. Research shows that infections and exposure to toxins such as HIV and streptococcus cause dementia. This HIV infection that makes its way to the brain is called encephalopathy which spreads itself through the brain leading to