I. Defining Abnormality
When discussing psychological disorders, the first step is to define what we mean by a disorder. How do we determine that something is wrong psychologically with a person? What constitutes abnormal? It's not as easy a matter as some people might think. Some might say, "Well, that person is odd." Being "odd" could mean that their behavior or thinking is rare; out of the statistical norm. But what about people who have high intelligence or are artistically gifted? Those traits aren't statistically frequent but we wouldn't call smart or artistic people abnormal. Being "odd" could also mean that a person's behavior isn't meeting certain social norms of the people around them. But those standards can vary between cultures (in some cultures, for instance, burping at the dinner table after eating is considered a compliment to the cook) and even within our own culture standards can vary between social groups (the behavioral excesses that might tolerated from a guitarist in a rock band would likely be unacceptable from an bank teller). So views of suitable social behavior aren't absolute. Some cognitive or perceptual distortions, such as hallucinations clearly are abnormal. But what about milder distortions or perceptions of reality like inflated egos or unusually high self-esteem? Some might say that feelings of personal distress like depression or anxiety are abnormal. But such feelings might be reasonable under some circumstances such as the death of a loved one or the loss of a job. Only one trait seems to be clearly important in all cases, and that is behavioral maladaptiveness. A clear sign of abnormal behavior or mental state is when an individual's behavior is destructive to themselves or their social group, such as family, friends or co-workers. More than any other sign harming the welfare of one's self or those close to one's self is most universally accepted as indicating an abnormal mental or behavioral state.

II. What's Normal?
In some ways the question of defining "abnormal" is simpler if we consider what we'd call "normal" when observing or categorizing the actions of others. One factor that seems common to people with "normal" psychological states is an efficient perception of reality, meaning that an individual can form reasonable and realistic appraisals of themselves and the world around them. Another factor is voluntary control over behavior. Many people may drink alcoholic beverages but not all people compulsively abuse alcohol, just as many people enjoy a fire in the fireplace on a cold night but not everybody compulsively sets fires like a pyromaniac might. Psychologically healthy people also have a sense of self-esteem and acceptance which enables them to be at ease around people and feel comfortable socially with others, to feel secure an unthreatened in social situations. But in addition to feeling good about themselves, they also are able to form affectionate relationships with others, whether it's with family, friends, neighbors, or colleagues. Psychologically healthy people are sensitive to others, able to form interpersonal bonds and don't make excessive personal demands on other people. Lastly, a psychologically healthy and "normal" person is able to maintain productivity. They are able to channel their energy and activity, even when the source of that energy is potentially negative (like anger, fear, or frustration), into useful and productive activity.

III. Classifying Abnormality: The DSM-IV
The official criteria and classification system used by mental health professionals is the Diagnostic and Statistical Manual (DSM) first published by the American Psychiatric Association in 1952. It has been revised several times. The revisions were undertaken because, as was suggested in the reference to social norms and abnormality, the formulation and application of the diagnostic criteria varies by social and cultural variables. The current edition is the DSM-IV (the IV referring to the fourth edition, released in 1994), the DSM-V is scheduled to be released in 2011. In the meantime a minimally revised version called the DSM-IV-TR (the TR referring to "text revision") was been released in 2000. This text-revised version of the DSM-IV did not change any of the criteria for diagnosis or classification system, only some of the narrative text was revised.

The DSM employs a five axis classification system to diagnose disorders and guide their treatment. Axis I lists acute clinical disorders (basically the problem that has brought the patient in for treatment). An example would be a phobia or depression. Axis II lists long-standing conditions, such as developmental disorders, learning disabilities, mental retardation, and personality disorders which might interact with the acute disorder on Axis I. Axis III lists medical conditions which may contribute to or underlie the Axis I disorder. For instance, open-heart surgery patients often experience depression due to the physical trauma of the major surgery. Axis IV lists social and environmental factors which may contribute to the disorder, such as a divorce, relocation (moving) or a death in the family. Axis V is a Global Assessment of Functioning which scores how well the patient copes with the disorder on a day-to-day basis in a variety of situations and environments.

In all, the DSM-IV-TR describes nearly 400 disorders. So, for our further discussion, we'll focus on several of the most commonly treated categories of disorders

IV. Anxiety Disorders
Anxiety disorders can be generally divided into those in which the source of the anxiety cannot be identified and those in which the source can be identified. Of those where the source is unidentifiable, we have generalized anxiety disorder (GAD) and panic disorder. In GAD, the feelings of anxiety and distress are free-floating. While sufferers may worry about their job, their finances, their health and their family, they may also worry over more common minor situations such as appointments, housework, haircuts and parking. Once developed, it is persistent and chronic with the sensations of anxiety and dread being experienced, essentially, constantly. In panic disorder (also called panic attack), the anxiety is very intense and debilitating, though it is confined to brief episodes. The sensations can be so severe that the sufferer may think they are having a heart attack. The attack can be triggered by a stressful situation, but often the attacks occur with no warning and for no apparent reason. However, for most of the sufferer’s day, they are usually fine.

When the source of the anxiety can be identified, it can be a specific object or situation or to an idea or to a traumatic event. When the anxiety is triggered by a specific object or situation the condition is called a phobia. All of us may be frightened of some objects or situations but we don’t necessarily have phobias, clinically speaking. In the case of a phobia, the fear is unreasonable and excessive, beyond the sufferer’s control to the point where it may interfere with daily life. Phobias can be simple (fear of a single stimulus such as heights or dogs), complex (a fear of a number of stimuli. In a fear of elevators, for example, fear of falling, being stuck between floors, tight enclosed places, losing self-control in front of others) or social (fear of what might occur in the company of others; for example, fear of blushing, losing self-control, public speaking, trembling, making a mistake).

When the source or trigger of the fear is an idea, the disorder is often Obsessive-Compulsive Disorder (OCD). In OCD, the sufferer experiences intrusive thoughts (the obsessions) which are the source of anxiety. However, the anxiety can only be relieved by performing an often ritualistic act (the compulsion). Common obsessions include germs or losing things. The compulsions for each of those may include washing for germs or arranging and grouping objects for losing things. However, the compulsion does not necessarily have to be logically related to the obsession. The only requirement is that, for whatever reason, it relieves the anxiety generated by the obsession.

When the anxiety source is related to a traumatic event in someone's life (Being in a war, natural disaster, car accident, house fire, the victim of a violent criminal attack) the categories are Posttraumatic Stress Disorder (PTSD) and Acute Stress Disorder (ASD). The hallmark of PTSD is the experience of vivid memory flashbacks (so vivid the sufferer may appear to be reliving the event) that are unpredictable in their frequency and occurrence. Other symptoms can include insomnia, nightmares, depression and emotional detachment. ASD is a similar disorder, but while PTSD is a long-lasting disorder, capable of persisting for years, ASD is only diagnosed during one month after the traumatic event. Also, ASD includes symptoms such as amnesia for aspects of the event, emotional detachment and an emotional numbing and depersonalization.

V. Mood Disorders
The category of mood disorders consists of clinical forms of depression. The two major categories of depression are major depression (also called unipolar depression) and bipolar disorder (also called manic-depression).

Major (unipolar) depression has a multitude of varieties under its "umbrella." It is possible though to organize some of the variations according to some characteristics. The first way to subdivide the unipolar depressive disorders is exogenous vs. endogenous. In exogenous depression, the disorder is triggered by events in the person's life such as a death of a loved one, a break-up or divorce, or a personal failure. In endogenous depression, there is no apparent triggering external event. The depression is due to a due presumably to either a genetic cause or a malfunction in brain chemistry, specifically, low levels of one or more of the monoamines. As one might surmise, endogenous depression usually responds very well to antidepressant medications. Exogenous depression can also respond to medication, but sometimes it can be resistant. Another form of unipolar depression is involutional depression which is mainly found in late middle-aged or elderly people and is thought to be related to aging and physiological and psychological changes associated (such as the decline of fitness, vigor and mental and physical abilities) with the aging process. Postpartum depression (PPD) is another form of depression that arguably has changes in the body's physiology as its putative cause. Some research suggests that the rapid sudden change in the body's hormonal profile when pregnancy comes to term and ends may cause postpartum depression, though other research points to lack of social support systems for the new parent. Seasonal affective disorder (SAD) is a form of unipolar depression that that is caused by insufficient exposure to bright sunlight. SAD is nonexistent in the tropics but is reported in northern latitudes during winter. It is thought that light sensitive neurons in the brain (the skull actually does transmit some light through the bone) that are part of the circuits involved in the hormonal regulation of the circadian sleep-wake cycle do not function normally and their resulting dysfunction is the source of the depression.

In contrast to unipolar depression, bipolar disorder involves a cyclical swing between mania (abnormally elevated mood and energy) and depression. However, the cycle between moods isn’t balanced with the depressive phase typically lasting much longer than the manic phase. The treatment of bipolar disorder is does not emphasize antidepressants, but rather compounds called mood stabilizers. The rationale for this strategy is the observation that if the manic phase can be prevented then the depressive phase does not follow. The most common treatment is salts of the metallic element, lithium. However, in some instances bipolar disorder does not respond to lithium. In those cases, some anticonvulsant medications seem to be effective.

VI. Schizophrenia
The word schizophrenia literally means "split mind" in Greek, but it has nothing to do with having multiple personalities. The split refers a "break" from reality. The hallmarks of the disease are disturbances of thought, attention, perception, and affect (emotion) accompanied by motor impairments and a withdrawal from reality that are severe enough to substantially impair ability to function normally and take care of one's self.

There are two forms of schizophrenia which share these hallmarks. One form is acute schizophrenia (also called reactive schizophrenia) which does not run in families. It may occur to an individual at any time in their life. It is precipitated by an emotionally traumatic or stressful event. It is not particularly responsive to medication. However, once an individual recovers they are not typically in danger of a relapse.

The other form is chronic schizophrenia (also called process schizophrenia) which does run in families and is heritable. It typically first presents itself in late adolescence or young adulthood. In its early stages it may even be misdiagnosed as OCD or Attention Deficit Disorder (ADD). However, once the sufferer becomes clearly psychotic and a diagnosis is made the disease is treatable with medication. The individual eventually goes into remission and regains clarity of thought, although, the disorder will recur periodically throughout the individual's life with the psychotic periods getting longer and the clear periods getting shorter and less frequent. However, in most cases medication is effective in treating the disorder.

Who is vulnerable? Well the disorder is relatively rare in the general population, occurring in less than 1% of all people. This disorder also does not discriminate between genders, men and women being equally susceptible. A family history of chronic schizophrenia is a risk factor. But when we focus on children who are at risk, having had one schizophrenic parent, these patterns are often present in children that develop schizophrenia as adults: They are more likely to have experienced birth complications, more likely to have been separated from their mothers at a young age, more likely to have had fathers hospitalized for a variety of psychological problems (alcoholism to schizophrenia), more likely to have displayed behavioral problems in school and more likely to have displayed spurts and lags in the development of visual and motor abilities. These factors cannot be shown to cause the disorder but they are correlated with a later diagnosis of schizophrenia.

Within schizophrenia there are two general clusters of symptoms, Type I (also called positive symptoms) and Type II (also called negative symptoms). Positive symptoms are called that because they are symptoms that are "added" (hence, the positive or "+") to a person's psychological state. These include hallucinations, delusions, bizarre behavior and confused thinking. Individuals who display primarily positive symptoms typically functioned well in social and educational setting before they started to display signs of the disorder. During their periods of clarity, they also function fairly normally and their symptoms respond very well to anti-psychotic medication. It is believed that these symptoms are related to overactive dopamine transmission. The rationale for this is that people who abuse stimulant drugs such as cocaine or amphetamine often develop a stimulant-induced psychosis that is virtually indistinguishable from schizophrenia. However, their symptoms subside after detoxification.

Negative symptoms are called negative because the reflect deficits from a person's normal psychological state. These include a poverty of speech, emotional unresponsiveness, seclusiveness and impaired attention. Individuals with primarily these symptoms have a poor history of social functioning prior to the onset of their disorder and resume those difficulties when they are in their clear phases. These symptoms are not responsive to anti-psychotic medication. It is believed that these symptoms are due to diffuse structural brain damage, presumably occurring before birth. Evidence for this hypothesis is the 1957 flu epidemic in Helsinki, Finland. In that epidemic, the children of pregnant women who were sick with the flu during their second trimester (a critical period of time in brain development) were at a higher risk of developing schizophrenia. In comparing positive and negative symptoms, it should be noted that there are rarely pure Type I or Type II chronic schizophrenics. Some patients have some of each type of symptom and the distribution and severity of the symptoms can change over the course of the illness.

Brain scans of schizophrenics show results consistent with brain damage and dopamine overactivity. Computerized axial tomography (CAT) and magnetic resonance imaging (MRI) scans which show the structure of the brain indicate much larger ventricles in schizophrenics compared to controls which suggests diffuse neuronal damage and cell loss. Positron emission tomography (PET) scans which can show brain metabolic activity show that while in a psychotic episode the frontal lobes of schizophrenics are less metabolically active than those of controls or even themselves when during a clear period or on their medication and symptom-free. Other PET scan studies have shown that schizophrenics also seem to have more D₂-like receptors than controls (The D₁ and D₅ receptors are similar and are called the D₁-like family. The D₂, D₃ and D₄ receptors are in the D₂-like family).

VII. Personality Disorders
Personality disorders are part of the DSM-IV axis II and they are characterized as rigid long-term patterns of thought and action. The DSM-IV recognizes 10 personality disorders but two, Borderline Personality Disorder (BPD) and Antisocial Personality Disorder (APD), have attracted the most research.

Individuals with BPD teeter between a variety of neurotic traits, display intense emotional instability and often display psychotic symptoms. Women are 3 times more likely than men to be diagnosed with BPD. These individuals have great difficulty in their personal relationships which are often tumultuous and unstable. They are often manipulative and display emotional neediness in order to avoid abandonment or the threat of abandonment, whether real or imagined. They are often great consumers of outpatient mental health services.

Those with APD often fit the label sociopath or psychopath. APD is more common in men than in women. In young boys, three traits are correlated with later diagnosis of APD: bedwetting, cruelty to animals and pyromania. Not all children who exhibit these traits develop APD but they are more common in the history of those with APD than they are in the general population. In severe cases of APD, it has been noted that the individuals seem to have no conscience, no guilt, no empathy or concern for others. They can be thrill-seeking and impulsive but show little physiological signs of anxiety or arousal. They can sometimes show signs of conscience, remorse, concern for others and can be quite charming. But these are insincere and actually well-mimicked behaviors to gain the fulfillment of their wishes. Con-artists and serial killers are often diagnosed with APD.

VIII. Dissociative Disorders
The dissociative disorders include Dissociative Amnesia, Dissociative Fugue and Dissociative Identity Disorder. The common thread in all these disorders is psychological dissociation, in which certain thoughts, emotions or memories are separated from awareness. In dissociative amnesia there is an inability to recall important personal information. The loss of memory is sudden and due to a psychologically stressful event. Its duration may be brief or prolonged and recovery can be sudden or gradual. Dissociative fugue is very similar in its symptoms, causes and duration. However, two things distinguish fugue from amnesia. First, fugue sufferers often travel away from their homes and assume new identities. Secondly, when the amnesic or fugue state ends, amnesia suffers recall the entire past. Fugue sufferers regain their old memories but their fugue memories are lost.

In dissociative identity disorder (DID; also referred to a multiple personality disorder) there is the presence of two or more distinct identities (each with its own relatively enduring pattern of perceiving, relating to, and thinking about the environment and self). The identities or personalities recurrently take control of the person's behavior. Often there is an inability to recall or share memories between personalities that occur when another personality is in control. The formation of multiple identities is argued to be a coping mechanism for a severe and early childhood psychological trauma.

IX. Infancy, Childhood, & Adolescence
Childhood diagnosed disorders include Attention Deficit with Hyperactivity Disorder (ADHD) and Pervasive Developmental Disorder (PDD, formerly called autism; though the term PDD now includes other related syndromes as well). ADHD can be broadly summarized as a disorder, which predominantly strikes male children and is characterized by inattention, impulsivity, and hyperactivity. Evidence suggests that children with ADHD have disturbances in behavior and cognitive function that are similar to those of patients with frontal lobe impairments. Learning impairments can be attributed to deficits in attention to stimuli or deficits in the expression of learned behavior. Impairments in working memory, both verbal and spatial, have also been reported. Working memory is thought to be essential for goal-directed learning and behavior management because it maintains a representation of events or stimuli after they have passed or are hidden from view. Brains of ADHD subjects have been reported to show structural abnormalities compared to non-ADHD subjects in the Frontal cortex and basal ganglia (FC/BG) circuit. ADHD subjects show reduced volumes in the frontal cortex, caudate and globus pallidus. Functional imaging findings also suggest hypofunction of the FC/BG circuit. Regional blood flow to the caudate and the white matter of the frontal lobes is reduced and in a behavioral (go/no go) task ADHD subjects exhibited atypical frontal-striatal activity compared to non-ADHD subjects. Overall, these findings support the view that ADHD is associated with impaired FC/BG activity. Indirect catecholamine agonists have been the primary pharmacological treatment for ADHD. Consistent with this treatment approach, molecular genetics have shown that alleles of specific dopamine related genes are associated with this disorder. Earlier studies implicated the D₂ receptor in ADHD and other impulsive disorders. More recent studies of family members diagnosed with ADHD have correlated variations of the dopamine transporter gene DAT₁ with the disorder. In related and unrelated ADHD subjects, variations of the D₄ receptor (part of the D₂-like family) have also been associated with ADHD. Children with autism/PDD show little to no responsiveness to others or the outside world. They have impaired verbal and nonverbal communication. They often display a highly restricted range of interests and are obsessed with rituals and order. That said, children with PDD display a range of abilities, skills and behaviors. Some are very high functioning. One individual with PDD, Temple Grandin is a Ph.D. in animal science and a professor at Colorado State University and is an internationally recognized authority on the design and construction of humane and low-stress livestock handling facilities. She describes her dealing with PDD and her obsession as a youth with ritual and order as an effort to deal with sensory stimulation. To her the sensory stimuli we can filter out were often intense and intrusive and her obsession with ritual and order was an attempt to cope with an experience that felt to her like sensory overload. Contrary to popular lore, individuals with PDD are not typically savants, that is, they do not posses extraordinary mental or artistic skills as was depicted in the movie, Rain Man. PDD and savant abilities are two separate conditions, though they can occur together. In fact, the real-life person that the movie Rain Man was based on, Kim Peek, is not autistic. He was born with several brain abnormalities including the lack of a corpus callosum which normally connects the two hemispheres of the brain. It is thought that his savant abilities are due to his brain's compensatory changes to deal with the lack of a corpus callosum.