Abnormal psychology is a part of psychology. People who study abnormal psychology are psychologists. They are scientists that investigate the mind using the scientific method. Different cultures tend to have different ideas of how strange (abnormal) any behaviour is considered. This tends to change over time within cultures, so people that live in a country at one time in history might consider abnormal what people who live in the same country consider normal years before or years later.

Abnormal psychology is often used to understand or to treat people with mental disorders to make life better for them. This is because abnormal behaviour is often defined as when someone is not able to change how they behave to fit different settings. This is often also used to define some mental disorders. When someone cannot change their behaviour to fit the people and situations around them when they need to, it can cause suffering, and the person may be uncomfortable when around people. Their behaviour can be unreasonable and hard to understand. Their behaviour can even be dangerous.

Not everyone with a mental disorder is unable to adjust to their surroundings. People who can change to fit their the environment around them more easily than most people can also have behaviour that is considered abnormal and might also have an easier life with the help of a psychologist.

History

Supernatural traditions
A supernatural belief is a belief in a force that is beyond scientific understanding. There are a lot of cultures that believe in supernatural events. These cultures include religious cultures, as well as the Ancient Chinese, Ancient Egyptians, Hebrews, and Ancient Greeks. These cultures have writings that say abnormal behaviour in the form of supernatural events created demons or Gods that would take over a person and act through those people. This was called possession. In the Roman Catholic Church, exorcisms were done to make these demons leave the body of the individuals they possessed. Exorcism involved prayer, noises and potions.p. 11 People who had abnormal behaviour were often told they were possessed.

In some cultures, trepanation was often used. This was when a hole was made in someone's head to release the "bad spirit".

Asylums
"Lunatic asylums" were buildings that kept patients that had abnormal behaviour. They became popular in Europe with the Madhouse Act of 1774, although they did exist before the Act. Asylums were meant to look after people who could not take care of themselves. But they were known for being cruel and abusive to their patients. The buildings were often dirty and not looked after very well.

During the late 1700s, William Tuke made a religious retreat for patients. This was a turn away from the horrors of mental asylums.p. 14 Also, in the late 1700s, Philippe Pinel started to encourage better treatment of the mentally insane.

Today the 18th-century lunatic asylum does not exist. Most of the asylums were closed in the late 1900s because of the invention of antipsychotic medicines. Today, there are psychiatric hospitals for people with mental illness. This includes Broadmoor Hospital, which houses some of Britain's the most dangerous criminals with mental illnesses.

Asylums in America
In the 1800s, Dorothea Dix fought against the bad treatment of patients in mental asylums. She started a "mental hygiene" group to encourage politicians to change the treatment of mental patients in the United States. When people became aware of the wrongdoing in mental asylums, money was raised to improve the treatment of patients and the asylums. Dix is thought to have helped to create 32 mental hospitals. By 1940 there were more than 400,000 patients living in mental asylums.

Most treatments were still cruel to patients and were not effective. The asylums were quickly becoming overcrowded. Mary Jane Ward wrote a book in 1946 called "The Snake Pit" that raised awareness of the inhumane treatment of mental patients.

The National Institute of Mental Health was created the same year. The organisation provided training and support for mental patients and workers that cared for them. The Hill-Burton Act was passed to give money to the mental health hospitals.

Later, the Community Health Services Act of 1963 was passed. This law which created outpatient buildings for patients to live at home rather than in hospitals. Rehabilitation and community care centers were also built under this act.p. 14

Deinstitutionalisation 
During the late 1900s, mental asylums were less accepted. The cruel treatment of patients and the overcrowding and ways of living were seen as not needed. Less money was being given to asylums. So many closed all around the world. The closing down of mental hospitals became known as deinstitutionalization. The movement from asylum to community was meant to help patients' development and recovery. The lack of good support programs meant that patients felt abandoned and found it hard to fit into normal life. This led to many becoming homeless.p. 16

Explaining abnormal behaviour
In the past there were three ways to explain abnormal behaviour. These were supernatural, biological, and psychological explanations. Western medicine no longer uses supernatural explanations. Instead we use biological and psychological explanations. Biological explanations use genetics and neuroscience to explain abnormal behaviours. The biological explanation is based on how the brain works and how genes change the way it works. Psychological explanations use how the mind works to explain abnormal behaviours.

Supernatural explanations
Early cultures believed that abnormal behaviour was from demons, spirits and astrology. Trepanation was when a hole was drilled in a person's head. This was done to let the spirits or demons out of the person's head.

Exorcism was practiced mainly by the Catholic Church. Exorcism was believed to ward the spirits out of the person that they possessed.

These practices were normal during the Middle Ages. This was when abnormal behaviour was thought to be a religious issue rather than a psychological one. Some abnormal behaviour was thought to be witchcraft. People accused of witchcraft were almost always punished for the acts. In many cases, the punishment was to be murdered.

Biological explanations
The Biological approach to explaining abnormal behaviour assumes that the behaviour can be explained by physical factors. Hippocrates was a man who lived during the 5th century and is thought by many to be the father of modern medicine. He did not accept that evil spirits or astronomy were the causes of psychological disorders. Hippocrates believed that there were natural causes for the disorders and appropriate treatments could be found. He focused on the "four humors" of the brain. He believed that the four humours must be balanced for healthy mental states and when one humour was stronger, various disorders would appear. To balance the humors, Hippocrates would tell patients to change their lifestyles.p. 11 There are now new ideas when talking about the biological explanations of psychological disorders. But, Hippocrates' focus on mental processes and clinical practice was a revolutionary concept.

Another Greek physician called Galen also took a scientific approach to the causes of psychological disorders. He divided them into physical and mental categories. Among Galen's causes were head injuries, alcohol abuse, and life experiences. During the 18th century, Galen's concepts influenced the medical industry. Galen's focus was on the biological causes for mental disorders.p. 13

Psychological explanations
Psychological explanations for abnormal behavior sometimes take a behavioral approach in which the positive behaviors are reinforced and negative ones are not. This approach is more focused on changing the actual behavior of a person than the true cause of it.

Sigmund Freud was one of the most popular psychological theorists of the 20th century. The method he used to study and treat patients was known as psychoanalysis. Methods of hypnosis by were used by Freud, but also by Franz Mesmer and physicians in the Nancy School. However, Freud attempted to have his patients confess their deepest, truest emotions, which was referred to as a catharsis. He would have his patients speak freely about themselves, in free association. Also he would conduct dream analysis where patients would record and discuss their dreams. Freud's work led to other great psychoanalytic theorists such as Carl Jung, Alfred Adler, and Harry Stack Sullivan. Wilhelm Wundt and William James were credited for opening up the first experimental psychology laboratories. This led to many studies and psychological methods, such as classical conditioning led by Ivan Pavlov and John B. Skinner, while Edward Thorndike and B. F. Skinner were the leaders of the study of operant conditioning.p. 18

Classification

DSM
The North American reference book used by psychiatrists and psychologists to diagnose and treat psychological disorders is known as the Diagnostic and Statistical Manual of Mental Disorders (DSM). It is produced by the American Psychiatric Association (APA). The most recent version was released in May of 2013 and is known as the DSM-5. The DSM is relied upon by clinicians, health insurance companies, medicine companies, and the legal system as a reference for understanding and identifying mental disorders. The DSM divides mental disorders into groups and provides descriptive signs and symptoms that define each disorder. In addition, it lists statistics for each disorder ranging from its frequency in the general population to the most effective form of treatment.

Before diagnosing an individual with a specific mental disorder, a professional must first determine whether that individual does in fact suffer from a mental disorder. The DSM defines a mental disorder as a condition that:

Is primarily psychological and alters behavior, personality, or motivation,
When in its full-blown state, causes stress, impairment in social functioning, or behavior that one would like to stop voluntarily because it poses a threat to physical health, and
Is distinct from other conditions, and is considered treatable.

When using the DSM, a complete psychiatric diagnosis is split up into five dimensions, called "axes", that relate to different characteristics of disability or disorder:

Axis I contains all categories of mental disorder except mental retardation and personality disorders. A disorder within this axis is similar to an illness or disease in general medicine, and includes depression, anxiety disorder, autism spectrum disorder, bipolar disorder, and anorexia.
Axis II contains mental retardation and personality disorders such as paranoid personality disorder, antisocial personality disorder, and obsessive-compulsive personality disorder. This axis contains a large number of disorders, all of which relate to how a person thinks and acts with the world.  
Axis III contains general medical conditions, minor medical conditions and any physical disorders of the individual. When the first three axes are used, relationships can be seen and it becomes easier for professionals to find the cause for mental disorder and treat a person effectively. 
Axis IV contains any environmental or social factors that could play a role in diagnosing an individual. Poor social relationships, the death of a loved one, or being fired from work are all stressful factors that may aid in the development of mental disorder.
Axis V is used by professionals for individuals under the age of 18. Children are graded on how well they currently handling their situation. The Global Assessment of Functioning used a scale of 0-100, but has been replaced in the DSM-5 by a survey and check box that is less subjective.

The separate axes of the DSM are often linked together in the development of mental disorders.

ICD-10
The International Statistical Classification of Diseases and Related Health Problems (ICD) was created by the World Health Organization (WHO) and is the universal diagnostic system for mental disorders. The ICD is approved by health officials from 193 WHO member countries, and is available for free on the internet. Its purpose is to help countries reduce the problems associated with mental disorders. The coding system used in the DSM is designed to be compatible with the system used in the ICD; however, some codes may not match because the two publications get revised at different times. The ICD-10 was made public in 1994; its most recent update occurred in 2010. Chapter 5 of the ICD-10 covers over 300 mental and behavioral disorders which are divided into the following categories:

F00-F09 Organic mental disorders
F10-F19 Mental and behavioral disorders caused by drug use
F20-F29 Schizophrenia and delusional disorders
F30-39 Mood disorders
F40-49 Neurotic, stress-related disorders
F50-59 Behavioral disorders linked with bodily disturbances and physical factors
F60-F69 Disorders of adult personality and behavior
F70-F79 Mental retardation
F80-F89 Disorders of psychological development
F90-F98 Behavioral and emotional disorders that develop during childhood
F99 Unspecified mental disorders

The Online ICD-10 can be found in its entirety here

Treatment

Psychoanalysis
Psychoanalysis is a form of therapy based on psychoanalytic theory. This theory states that human behavior is controlled by unconscious forces such as instinct and that there is no such thing as free will. Many ideas found in the Psychoanalytic theory can be traced back to the famous psychologist Sigmund Freud. Freud believed mental disorders are a result of repressed memories and emotions from childhood; psychoanalysis is designed to search for these hidden memories and emotions and bring them to the patient's attention. Techniques such as hypnosis are used to tap into the unconscious mind with the hopes that the source of the disturbance is found. Freud also believed dreams had hidden meanings, and often asked patients to record their dreams for analysis. Because of the lack of scientific evidence supporting most Freudian ideas, psychoanalysis is rarely used by clinical psychologists and has been replaced by more effective forms of therapy.

Behavioral therapy
Behavior therapy is based on the theory of behaviorism, which states that all human behavior is a result of a stimulus and reinforcement. Famous behaviorists include James Watson, B.F. Skinner, and Joseph Wolpe. The goal of this therapy is to increase one's positive or socially reinforcing behavior. Behavior therapy can be broken down into three areas:
Applied behavior analysis (ABA) uses a form of operant conditioning where positive reinforcement is used to modify behavior.
Cognitive behavioral therapy (CBT) focuses on conditioning the negative thoughts and feelings behind patients' behavior in order to alter that behavior.
 Social learning theory is used in the treatment and understanding of anxiety disorders. It goes beyond the traditional classical conditioning assumption that fear and anxiety must be learned directly; social learning theory suggests that a child could acquire a fear of snakes, for example, by observing a family member show fear in response to snakes.

Humanistic therapy 
Humanistic therapy is a method taken from Carl Rogers, which aims to focus on a client as a human rather than the problem that they have. A therapist can adjust the environment and mood of a session in a way that mimics normal conversation. This often helps the patient realize the issues they have, and share them with the therapist more successfully than in a traditional counseling session. Humanistic therapy creates an effective means of getting to the source of a problem and treating it properly.

Roger's own term was "client-centered therapy", which has the idea that the therapist is helping the client to become a genuine psychological adult.

References

Human behavior
Psychology