A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitting, or occur as single episodes. Many disorders have been described, with signs and symptoms that vary widely between specific disorders. Such disorders may be diagnosed by a mental health professional, usually a clinical psychologist or psychiatrist.
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations, delusions, paranoia, and disorganized thinking. Other symptoms include social withdrawal, decreased emotional expression, and apathy. Symptoms typically come on gradually, begin in young adulthood, and in many cases never resolve. There is no objective diagnostic test; the diagnosis is used to describe observed behavior that may stem from numerous different causes. Besides observed behavior, doctors will also take a history that includes the person's reported experiences, and reports of others familiar with the person, when making a diagnosis. To diagnose someone with schizophrenia, doctors are supposed to confirm that symptoms and functional impairment are present for six months (DSM-5) or one month (ICD-11). Many people with schizophrenia have other mental disorders, especially substance use disorders, depressive disorders, anxiety disorders, and obsessive–compulsive disorder.
Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics and in content fields, from biology to psychology. Twin studies are part of the broader methodology used in behavior genetics, which uses all data that are genetically informative – siblings studies, adoption studies, pedigree, etc. These studies have been used to track traits ranging from personal behavior to the presentation of severe mental illnesses such as schizophrenia.
Paul Eugen Bleuler was a Swiss psychiatrist and humanist most notable for his contributions to the understanding of mental illness. He coined several psychiatric terms including "schizophrenia", "schizoid", "autism", depth psychology and what Sigmund Freud called "Bleuler's happily chosen term ambivalence".
Schizotypal personality disorder, also known as schizotypal disorder, is a mental and behavioural disorder. DSM classification describes the disorder specifically as a personality disorder characterized by thought disorder, paranoia, a characteristic form of social anxiety, derealization, transient psychosis, and unconventional beliefs. People with this disorder feel pronounced discomfort in forming and maintaining social connections with other people, primarily due to the belief that other people harbour negative thoughts and views about them. Peculiar speech mannerisms and socially unexpected modes of dress are also characteristic. Schizotypal people may react oddly in conversations, not respond, or talk to themselves. They frequently interpret situations as being strange or having unusual meaning for them; paranormal and superstitious beliefs are common. Schizotypal people usually disagree with the suggestion their thoughts and behaviour are a 'disorder', and seek medical attention for depression or anxiety instead. Schizotypal personality disorder occurs in approximately 4% of the general population and is more commonly diagnosed in males.
Human behaviour genetics is an interdisciplinary subfield of behaviour genetics that studies the role of genetic and environmental influences on human behaviour. Classically, human behavioural geneticists have studied the inheritance of behavioural traits. The field was originally focused on determining the importance of genetic influences on human behaviour. It has evolved to address more complex questions such as: how important are genetic and/or environmental influences on various human behavioural traits; to what extent do the same genetic and/or environmental influences impact the overlap between human behavioural traits; how do genetic and/or environmental influences on behaviour change across development; and what environmental factors moderate the importance of genetic effects on human behaviour. The field is interdisciplinary, and draws from genetics, psychology, and statistics. Most recently, the field has moved into the area of statistical genetics, with many behavioural geneticists also involved in efforts to identify the specific genes involved in human behaviour, and to understand how the effects associated with these genes changes across time, and in conjunction with the environment.
Neurodevelopmental disorders are a group of disorders that affect the development of the nervous system, leading to abnormal brain function which may affect emotion, learning ability, self-control, and memory. The effects of neurodevelopmental disorders tend to last for a person's lifetime.
The heritability of autism is the proportion of differences in expression of autism that can be explained by genetic variation; if the heritability of a condition is high, then the condition is considered to be primarily genetic. Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether autism spectrum disorder (ASD) is explained more by multigene interactions or by rare mutations with major effects.
The trauma model of mental disorders, or trauma model of psychopathology, emphasises the effects of physical, sexual and psychological trauma as key causal factors in the development of psychiatric disorders, including depression and anxiety as well as psychosis, whether the trauma is experienced in childhood or adulthood. It conceptualises victims as having understandable reactions to traumatic events rather than suffering from mental illness.
The biopsychiatry controversy is a dispute over which viewpoint should predominate and form a basis of psychiatric theory and practice. The debate is a criticism of a claimed strict biological view of psychiatric thinking. Its critics include disparate groups such as the antipsychiatry movement and some academics.
Psychiatric genetics is a subfield of behavioral neurogenetics and behavioral genetics which studies the role of genetics in the development of mental disorders. The basic principle behind psychiatric genetics is that genetic polymorphisms are part of the causation of psychiatric disorders.
James Jay Joseph is an American clinical psychologist and author. He practices psychology in the San Francisco Bay Area. He is known for his criticisms of behavior genetics and twin studies in psychology and psychiatry. His view, as he articulated in his 2003 book The Gene Illusion, is that such research is so flawed as to render all of its results completely meaningless.
Risk factors of schizophrenia include many genetic and environmental phenomena. The prevailing model of schizophrenia is that of a special neurodevelopmental disorder with no precise boundary or single cause. Schizophrenia is thought to develop from very complex gene–environment interactions with vulnerability factors. The interactions of these risk factors are intricate, as numerous and diverse medical insults from conception to adulthood can be involved. The combination of genetic and environmental factors leads to deficits in the neural circuits that affect sensory input and cognitive functions. Historically, this theory has been broadly accepted but impossible to prove given ethical limitations. The first definitive proof that schizophrenia arises from multiple biological changes in the brain was recently established in human tissue grown from patient stem cells, where the complexity of disease was found to be "even more complex than currently accepted" due to cell-by-cell encoding of schizophrenia-related neuropathology.
Irving Isadore Gottesman was an American professor of psychology who devoted most of his career to the study of the genetics of schizophrenia. He wrote 17 books and more than 290 other publications, mostly on schizophrenia and behavioral genetics, and created the first academic program on behavioral genetics in the United States. He won awards such as the Hofheimer Prize for Research, the highest award from the American Psychiatric Association for psychiatric research. Lastly, Gottesman was a professor in the psychology department at the University of Minnesota, where he received his Ph.D.
Sarnoff Andrei Mednick, pioneered the prospective high-risk, longitudinal study to investigate the etiology (causes) of psychopathology, or mental disorders. His emphasis was on schizophrenia. He made significant contributions to the study of creativity, psychopathy, alcoholism and suicide in schizophrenia. He was a Professor Emeritus at The University of Southern California, where he had been a tenured professor since the early '70s and remained highly active in his eighties. Mednick was the first scientist to revisit the genetic basis of mental disorders, following the era of eugenics. He was the recipient of the Joseph Zubin Award in 1996, with more than 300 peer-reviewed publications on the topic.
Social constructionism, a branch of sociology, queries commonly held views on the nature of reality, touching on themes of normality and abnormality within the context of power and oppression in societal structures.
The imprinted brain hypothesis is an unsubstantiated hypothesis in evolutionary psychology regarding the causes of autism spectrum and schizophrenia spectrum disorders, first presented by Bernard Crespi and Christopher Badcock in 2008. It claims that certain autistic and schizotypal traits are opposites, and that this implies the etiology of the two conditions must be at odds.
The evolution of schizophrenia refers to the theory of natural selection working in favor of selecting traits that are characteristic of the disorder. Positive symptoms are features that are not present in healthy individuals but appear as a result of the disease process. These include visual and/or auditory hallucinations, delusions, paranoia, and major thought disorders. Negative symptoms refer to features that are normally present but are reduced or absent as a result of the disease process, including social withdrawal, apathy, anhedonia, alogia, and behavioral perseveration. Cognitive symptoms of schizophrenia involve disturbances in executive functions, working memory impairment, and inability to sustain attention.
Evolutionary psychiatry, also known as Darwinian psychiatry, is a theoretical approach to psychiatry that aims to explain psychiatric disorders in evolutionary terms. A branch of the field of evolutionary medicine, it is distinct from the medical practise of psychiatry in its emphasis on providing scientific explanations rather than treatments for mental disorder. This often concerns questions of ultimate causation. For example, psychiatric genetics may discover genes associated with mental disorders, but evolutionary psychiatry asks why those genes persist in the population. Other core questions in evolutionary psychiatry are why heritable mental disorders are so common how to distinguish mental function and dysfunction, and whether certain forms of suffering conveyed an adaptive advantage. Disorders commonly considered are depression, anxiety, schizophrenia, autism, eating disorders, and others. Key explanatory concepts are of evolutionary mismatch and the fact that evolution is guided by reproductive success rather than health or wellbeing. Rather than providing an alternative account of the cause of mental disorder, evolutionary psychiatry seeks to integrate findings from traditional schools of psychology and psychiatry such as social psychology, behaviourism, biological psychiatry and psychoanalysis into a holistic account related to evolutionary biology. In this sense, it aims to meet the criteria of a Kuhnian paradigm shift.
Adoption studies are one of the classic research methods of behavioral genetics, used to estimate the degree to which variation in a trait is due to environmental and genetic influences. Adoption studies are typically used as well as twin studies when estimating heritability. The two types of adoption study designs are the Adoptee's method, and the Familial method. The most powerful form of adoption studies compares pairs of genetically identical monozygotic identical (MZA) twins who are adopted into different families. Adoption studies have pinpointed that some traits are linked to genetics; for example, schizophrenia, IQ, and criminality. However, other compound factors, such as age and environment, have an impact as well.
