The term somatization has been used to refer to a wide variety of clinical phenomena. From a more traditional view it could be defined as the inability to express emotional distress, the somatic symptoms being a “distress idiom.” Another point of view would define somatization as somatic complaints in the presence of an anxiety disorder or an underlying depression. The third view presents somatization as the presence of somatic symptoms that do not have a clear medical explanation. Each of the three ways used to define somatization may identify different groups of patients. Several studies indicate varying prevalence rates, from 0.2 % to 2 % in women and less than 0.2 % in men. Individuals with somatization disorder are usually young women, who describe their symptoms in a striking and exaggerated way. They tell of multiple, relevant, somatic complaints that affect various systems. The majority of individuals with this disorder report the presence of nausea and bloating. The disease is diagnosed before the age of 25, and the first symptoms can start to occur during adolescence; in women menstrual irregularities constitute one of the signs that manifest it more promptly. Sexual symptoms are often associated with marital conflict. The reasons why these patients are often seen in mental health facilities are because of the presence of significant symptoms of anxiety and depression. There is a positive correlation between depression and somatic symptoms [28], constituting in certain studies up to 85 % [29]. From this close relationship the term “masked depression” arises, which explains the manifestation of a depressive disorder primarily by physical symptoms, which are more intense and severe than the psychic symptoms [30]. In the work of Kirmayer and Robins [31], only 21 % of the patients presenting an anxious or depressive disorder communicate mental symptoms to their general physician.

Disorders related to substance abuse are frequently associated with somatization disorder, as are histrionic personality, and limited and antisocial disorders. It is important to differentiate between somatization disorder and simulation and factitious disorders. In the latter, unlike with somatization, the patient exerts control of his symptoms either by faking them or by self-inducing them.

Pain is defined by the International Association for the study of Pain (IASP) as “an unpleasant sensation and emotional experience, associated with a present or potential damage in tissues,” and it is a subjective experience only recognized by the patient who can be believed or not by the treating physician. Pain disorder is defined in the CIE as “a persistent pain without a clear medical explanation”; it differs from the DSM definition, which believes that “psychological factors play an important role in the onset, severity, exacerbation or the persistence of pain.” It is more frequent in women with a ratio of 2 to 1.This disorder can appear at any age. Women seem to experience certain types of chronic pain, such as headaches and musculoskeletal pain, more frequently than men. The pain may seriously alter several aspects of daily life. Unemployment, disability, and family problems have been frequently observed among individuals who suffer from chronic forms of pain disorder.

Dependence or abuse of iatrogenic opiates and/or benzodiazepines may occur; therefore, the use of these drugs should be avoided. Individuals suffering from pain associated with severe depression or related to a terminal illness, primarily cancer, are at an increased risk of suicide. Patients with recurrent acute pain or chronic pain are convinced that somewhere there is a health professional who has the healing method for their pain. There is no voluntary control of the symptoms and it is often difficult to find a psychological factor in the psychogenesis of pain. Comorbidity with anxiety and depression as well as with conversion disorders is very common.

It is historically referred to as hysterical neurosis of conversion. The essential characteristic of conversion disorder is the presence of symptoms or deficits that affect the motor or sensory functions and which suggest a neurological disorder or any other medical illness. Conversion symptoms are related to voluntary or sensory motor activity, and therefore are called “pseudo-neurological.” Typical motor symptoms are disturbances of coordination and balance, paralysis or localized muscle weakness, localized hoarseness, difficulty swallowing, sensation of a lump in the throat, and urinary retention. The sensory type symptoms tend to be loss of touch and painful sensitivity, diplopia, blindness, deafness, and hallucinations. Crisis or seizures may also occur. The less medical knowledge the patient has, the more implausible are his referring symptoms. Individuals with symptoms of conversion may manifest la belle indifference (a relative lack of concern about the nature or the implications of the symptoms) or present attitudes of a dramatic or histrionic type. Owing to the easy suggestibility of these individuals, their symptoms may be modified or may disappear according to external stimuli; however, it must be kept in mind that this is not specific to conversion disorder and that it can occur in different medical diseases. It is common for symptoms to appear after a situation of extreme psychosocial stress.

Various specific somatic syndromes have been described that are defined by somatic symptoms; these are part of entities such as fibromyalgia, irritable bowel syndrome or chronic fatigue syndrome. Most of these syndromes occur more frequently in women than in men [32]. Primary care studies have found that several of these syndromes are associated with symptoms of anxiety and depression [33].

The essential feature of hypochondriasis is worry and fear of suffering, or the conviction of having a serious illness, from the erroneous interpretation of one or more signs or somatic symptoms. It usually starts between the ages of 20 and 30, being somewhat more frequent in women and having a chronic evolution. The fact that it is more frequent in women may have to do with the high proportion of women being treated in the medical facilities.

The physical examinations and different tests that these patients undergo because of the etiology of their symptoms are negative. Despite these negative results, patients are persistent in their belief and are alarmed when there is any indicative sign of possible illness, constantly observing their bodies. Often, patients tend to present their clinical history in a very detailed and extensive manner. The presence of “medical pilgrimages” (doctor shopping) and the deterioration of the patient–physician relationship, with frustration and anger on both sides, are frequent. Sometimes these patients believe that they do not receive appropriate care and refuse to be sent to mental health centers. People suffering from this disorder may be alarmed when reading or hearing about diseases, with the news that someone has been ill or even by observing what is happening in their own body. Being concerned about the disease often becomes the individual’s central feature of self-perception, in a repeated conversation subject, and in response to a stressful situation. It is important to differentiate between hypochondriasis and apprehensive people. In hypochondriasis discomfort is significant, affecting employment, social life, or other important areas in the person’s life. Rates of psychiatric comorbidity of hypochondria are high, up to 80 %, including anxious disorders, depressive disorders, and personality disorders [34, 35]. In the latter case, many authors argue that hypochondria is really a pattern of dysfunctional personality with a tendency to interpret somatic sensations [36].