A self-disorder, also called ipseity disturbance, is a psychological phenomenon of disruption or diminishing of a person's sense of minimal (or basic) self. The sense of minimal self refers to the very basic sense of having experiences that are one's own; it has no properties, unlike the more extended sense of self, the narrative self, which is characterized by the person's reflections on themselves as a person, things they like, their identity, and other aspects that are the result of reflection on one's self. Disturbances in the sense of minimal self, as measured by the Examination of Anomalous Self-Experience (EASE), aggregate in the schizophrenia spectrum disorders, to include schizotypal personality disorder, and distinguish them from other conditions such as psychotic bipolar disorder and borderline personality disorder.

Depersonalization is the third most common psychological symptom, after feelings of anxiety and feelings of depression. Depersonalization is a symptom of anxiety disorders, such as panic disorder. It can also accompany sleep deprivation (often occurring when suffering from jet lag), migraine, epilepsy (especially temporal lobe epilepsy), obsessive-compulsive disorder, stress, anxiety, and some cases of low latent inhibition. Interoceptive exposure is a non-pharmacological method that can be used to induce depersonalization.

A similar and overlapping concept called ipseity disturbance (ipse is Latin for "self" or "itself") may be part of the core process of schizophrenia spectrum disorders. However, specific to the schizophrenia spectrum seems to be "a "dis"location of first-person perspective such that self and other or self and world may seem to be non-distinguishable, or in which the individual self or field of consciousness takes on an inordinate significance in relation to the objective or intersubjective world" (emphasis in original).

For the purposes of evaluation and measurement depersonalisation can be conceived of as a construct and scales are now available to map its dimensions in time and space. A study of undergraduate students found that individuals high on the depersonalization/derealization subscale of the Dissociative Experiences Scale exhibited a more pronounced cortisol response. Individuals high on the absorption subscale, which measures a subject's experiences of concentration to the exclusion of awareness of other events, showed weaker cortisol responses.

Individuals who experience depersonalization feel divorced from their own personal self by sensing their body sensations, feelings, emotions, behaviors etc. as not belonging to the same person or identity. Often a person who has experienced depersonalization claims that things seem unreal or hazy. Also, a recognition of a self breaks down (hence the name). Depersonalization can result in very high anxiety levels, which further increase these perceptions.

Depersonalization is a subjective experience of unreality in one's self, while derealization is unreality of the outside world. Although most authors currently regard depersonalization (self) and derealization (surroundings) as independent constructs, many do not want to separate derealization from depersonalization.

An adjustment disorder (AD)—sometimes called exogenous, reactive, or situational depression—occurs when an individual is unable to adjust to or cope with a particular stress or a major life event. Since people with this disorder normally have symptoms that depressed people do, such as general loss of interest, feelings of hopelessness and crying, this disorder is sometimes known as situational depression. Unlike major depression, the disorder is caused by an outside stressor and generally resolves once the individual is able to adapt to the situation. One hypothesis about AD is that it may represent a sub-threshold clinical syndrome.

The condition is different from anxiety disorder, which lacks the presence of a stressor, or post-traumatic stress disorder and acute stress disorder, which usually are associated with a more intense stressor.

Common characteristics of AD include mild depressive symptoms, anxiety symptoms, and traumatic stress symptoms or a combination of the three. There are nine types of AD listed in the DSM-III-R. According to the DSM-IV-TR, there are six types of AD, which are characterized by the following predominant symptoms: depressed mood, anxiety, mixed depression and anxiety, disturbance of conduct, mixed disturbance of emotions and conduct, and unspecified. However, the criteria for these symptoms are not specified in greater detail. AD may be acute or chronic, depending on whether it lasts more or less than six months. According to the DSM-IV-TR, if the AD lasts less than 6 months, then it may be considered acute. If it lasts more than six months, it may be considered chronic. Moreover, the symptoms cannot last longer than six months after the stressor(s), or its consequences, have terminated. Diagnosis of AD is quite common; there is an estimated incidence of 5%–21% among psychiatric consultation services for adults. Adult women are diagnosed twice as often as are adult men. Among children and adolescents, girls and boys are equally likely to receive this diagnosis. AD was introduced into the psychiatric classification systems almost 30 years ago, but similar syndromes were recognized for many years before that.

Dissociative disorder not otherwise specified (DDNOS) is a mental health diagnosis for pathological dissociation that matches the DSM-5 criteria for a dissociative disorder, but does not fit the full criteria for any of the specifically identified subtypes, which include dissociative identity disorder, dissociative amnesia, and depersonalization/derealization disorder. The International Statistical Classification of Diseases and Related Health Problems (ICD-10) refers to the diagnosis as "Other dissociative and conversion disorders".

Examples of DDNOS include chronic and recurrent syndromes of mixed dissociative symptoms, identity disturbance due to prolonged and intense coercive persuasion, disorders similar to dissociative identity disorder, acute dissociative reactions to stressful events, and dissociative trance.

DDNOS is the most common dissociative disorder and is diagnosed in 40% of dissociative disorder cases. It is often co-morbid with other mental illnesses such as complex posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, personality disorders, substance abuse disorders and eating disorders.

International Statistical Classification of Diseases and Related Health Problems, mostly known as "ICD", assigns codes to classify diseases, symptoms, complaints, social behaviors, injuries, and such medical-related findings.

ICD 10 classifies adjustment disorders under F40-F48 and under neurotic, stress-related and somatoform disorders.

The minimal self has been likened to a "flame that enlightens its surroundings and thereby itself." Unlike the extended self, which is composed of properties such as the person's identity, the person's narrative, and other aspects that can be gleaned from reflection, the minimal self has no properties, but refers to the "mine-ness" "given-ness" of experience, that the experiences are that of the person having them in that person's stream of consciousness. These experiences that are part of the minimal self are normally "tacit" and implied, requiring no reflection on the part of the person experiencing to know that the experience is theirs. The minimal self cannot be further elaborated and normally one cannot grasp it upon reflection. The minimal self goes hand-in-hand with immersion in the shared social world, such that "[t]he world is always pregiven, ie, tacitly grasped as a self-evident background of all experiencing and meaning." This is the self-world structure.

De Warren gives an example of the minimal self combined with immersion in the shared social world: "When looking at this tree in my backyard, my consciousness is directed toward the tree and not toward my own act of perception. I am, however, aware of myself as perceiving this tree, yet this self-awareness (or self-consciousness) is not itself thematic." The focus is normally on the tree itself, not on the person's own act of seeing the tree: to know that one is seeing the tree does not require an act of reflection.

Hyperreligiosity is characterized by an increased tendency to report spiritual, religious or mystical experiences, religious delusions, rigid legalistic thoughts, and extravagant expression of religiosity. Hyperreligiosity may also include religious hallucinations.

Hyperreligiosity is a psychiatric disturbance in which a person experiences intense religious beliefs or experiences that interfere with normal functioning. Hyperreligiosity generally includes abnormal beliefs and a focus on religious content, which interferes with work and social functioning. Hyperreligiosity may occur in a variety of disorders including epilepsy, psychotic disorders and frontotemporal lobar degeneration. Hyperreligiosity is a symptom of Geschwind syndrome, which is associated with temporal lobe epilepsy.

Patients suffering traumatic brain injury experience profound disturbance of the basic functions of the cognitive, behavioral, emotional and intellectual systems. Such patients' ability to regulate interaction between the ego and the external world is greatly diminished and they typically exhibit inflexible, concrete and sometimes inappropriate behaviors.

Emotional and behavioral disorders (EBD; sometimes called emotional disturbance or serious emotional disturbance) refer to a disability classification used in educational settings that allows educational institutions to provide special education and related services to students that have poor social or academic adjustment that cannot be better explained by biological abnormalities or a developmental disability.

The classification is often given to students that need individualized behavior supports to receive a free and appropriate public education, but would not be eligible for an individualized education program under another disability category of the Individuals with Disabilities Education Act (IDEA).

Hyperprosexia, and paraprosexia are closely related medical and neuro-psychiatric phenomena associated with attention and concentration. They typically occur in patients suffering traumatic brain injuries.

- "Aprosexia" is an abnormal inability to pay attention, characterized by a near-complete indifference to everything.

- "Hyperprosexia" is the abnormal state in which a person concentrates on one thing to the exclusion of everything else.

- "Paraprosexia" is the inability to pay attention to any one thing (a state of constant distraction).

Late life depression refers to a major depressive episode occurring for the first time in an older person (usually over 50 or 60 years of age). Concurrent medical problems and lower functional expectations of elderly patients often obscure the degree of impairment. Typically, elderly patients with depression do not report depressed mood, but instead present with less specific symptoms such as insomnia, anorexia, and fatigue. Elderly persons sometimes dismiss less severe depression as an acceptable response to life stress or a normal part of aging.

To meet criteria for a major depressive episode, a patient must have 5 of these 9 symptoms nearly every day for at least 2 weeks.

1. Depressed or sad mood

2. Anhedonia (loss of interest in pleasurable activities)

3. Sleep disturbance (increased or decreased sleep)

4. Appetite disturbance (increased or decreased appetite) typically with weight change

5. Energy disturbance (increased or decreased energy/activity level), usually fatigue

6. Poor memory and/or concentration

7. Feelings of guilt or worthlessness

8. Psychomotor retardation or agitation (a change in mental and physical speed perceived by other people)

9. Thoughts of wishing you were dead; suicidal ideation or suicide attempts

The IDEA requires that a student must exhibit one or more of the following characteristics over a long duration, and to a marked degree that adversely affects their educational performance, to receive an EBD classification:

- Difficulty to learn that cannot be explained by intellectual, sensory, or health factors.

- Difficulty to build or maintain satisfactory interpersonal relationships with peers and teachers.

- Inappropriate types of behavior (acting out against self or others) or feelings (expresses the need to harm self or others, low self-worth, etc.) under normal circumstances.

- A general pervasive mood of unhappiness or depression.

- A tendency to develop physical symptoms or fears associated with personal or school problems.

The term "EBD" includes students diagnosed with schizophrenia, but does not apply to students who are "socially maladjusted", unless it is determined that they also meet the criteria for an EBD classification.

Courtship disorder is a theoretical construct in sexology in which a certain set of paraphilias are seen as specific instances of anomalous courtship instincts in men. The specific paraphilias are biastophilia (paraphilic rape), exhibitionism, frotteurism, telephone scatologia, and voyeurism. According to the "courtship disorder hypothesis", there is a species-typical courtship process in human males consisting of four phases, and anomalies in different phases result in one of these paraphilic sexual interests. That is, instead of being independent paraphilias, this theory sees these sexual interests as individual symptoms of a single underlying disorder.

The history of disturbance in pseudodementia is often short and abrupt onset, while dementia is more often insidious. Clinically, people with pseudodementia differ from those with true dementia when their memory is tested. They will often answer that they don't know the answer to a question, and their attention and concentration are often intact, and they may appear upset or distressed. Those with true dementia will often give wrong answers, have poor attention and concentration, and appear indifferent or unconcerned.

Investigations such as SPECT imaging of the brain show reduced blood flow in areas of the brain in people with Alzheimer's disease, compared with a more normal blood flow in those with pseudodementia.

Pseudodementia is a phenotype approximated by a wide variety of underlying disorders (1). Data indicate that some of the disorders that can convert to a pseudodementia-like presentation include depression (mood), schizophrenia, mania, dissociative disorders, Ganser syndrome, conversion reaction, and psychoactive drugs (2). Although the frequency distribution of disorders presenting as pseudodementia remains unclear, what is clear is that depressive pseudodementia, synonymously referred to as depressive dementia(3) or major depression with depressive dementia (4), represents a major subclass of the overarching category of pseudodementia (4).

It has long been observed that in the differential diagnosis between dementia and pseudodementia, depressive pseudodementia appears to be the single most difficult disorder to distinguish from nosologically established "organic" categories of dementia(5), especially degenerative dementia of the Alzheimer type (6).

Depressive Pseudodementia is a syndrome seen in older people in which they exhibit symptoms consistent with dementia but the cause is actually depression.

Older people with predominant cognitive symptoms such as loss of memory, and vagueness, as well as prominent slowing of movement and reduced or slowed speech, were sometimes misdiagnosed as having dementia when further investigation showed they were suffering from a major depressive episode. This was an important distinction as the former was untreatable and progressive and the latter treatable with antidepressant therapy or electroconvulsive therapy or both. In contrast to major depression, dementia is a progressive neurodegenerative syndrome involving a pervasive impairment of higher cortical functions resulting from widespread brain pathology.

Sexual maturation disorder is a disorder of anxiety or depression related to an uncertainty about one's gender identity or sexual orientation. The World Health Organization (WHO) lists sexual maturation disorder in the ICD-10, under "Psychological and behavioural disorders associated with sexual development and orientation".

Sexual orientation, by itself, is not a disorder and is not classified under this heading. It differs from ego-dystonic sexual orientation where the sexual orientation or gender identity is repressed or denied.

The fifth edition of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5) renamed "Feeding Disorder of Infancy or Early Childhood" to Avoidant/Restrictive Food Intake Disorder, and broadened the diagnostic criteria. Previously defined as a disorder exclusive to children and adolescents, the DSM-5 broadened the disorder to include adults who limit their eating and are affected by related physiological or psychological problems, but who do not fall under the definition of another eating disorder.

The DSM-5 defines the following diagnostic criteria:

- Disturbance in eating or feeding, as evidenced by one or more of:

- Substantial weight loss (or, in children, absence of expected weight gain)

- Nutritional deficiency

- Dependence on a feeding tube or dietary supplements

- Significant psychosocial interference

- Disturbance not due to unavailability of food, or to observation of cultural norms

- Disturbance not due to anorexia nervosa or bulimia nervosa, and no evidence of disturbance in experience of body shape or weight

- Disturbance not better explained by another medical condition or mental disorder, or when occurring concurrently with another condition, the disturbance exceeds what is normally caused by that condition

In previous years, the DSM was not inclusive in recognizing all of the challenges associated with feeding and eating disorders in 3 main domains:

- Eating Disorders Not Otherwise Specified (EDNOS) was an all-inclusive, placeholder group for all individuals that presented challenges with feeding

- The category of Feeding Disorder of Infancy/ Early Childhood was noted to be too broad, limiting specification when treating these behaviors

- There are children and youth who present feeding challenges but do not fit within any existing categories to date

Children are often picky eaters, this does not necessarily mean they meet the criteria for an ARFID diagnosis. In addition, self-identification as having ARFID may contribute to ARFID.

The determination of the cause of ARFID has been difficult due to the lack of diagnostic criteria and concrete definition. However, many have proposed other mental disorders that are comorbid with ARFID.

There are different kinds of 'sub-categories' identified for ARFID:

- Sensory-based avoidance, where the individual refuses food intake based on smell, texture, color, brand, presentation

- A lack of interest in consuming the food, or tolerating it nearby

- Food being associated with fear-evoking stimuli that have developed through a learned history

According to the "courtship disorder hypothesis", there is a species-typical courtship process in humans consisting of four phases. These phases are: "(1) looking for and appraising potential sexual partners; (2) pretactile interaction with those partners, such as by smiling at and talking to them; (3) tactile interaction with them, such as by embracing or petting; (4) and then sexual intercourse."

The associations between these phases and these paraphilias were first outlined by Kurt Freund, the originator of the theory: A disturbance of the search phase of courtship manifests as voyeurism, a disturbance of the pretactile interaction phase manifests as exhibitionism or telephone scatologia, a disturbance of the tactile interaction phase manifests as toucheurism or frotteurism, and the absence of the courtship behavior phases manifests as paraphilic rape (i.e., biastophilia). According to Freund, these paraphilias "can be conceptualized as a preference for a pattern of behavior or erotic fantasy in which one of these four phases of sexual interaction is intensified and distorted to such an extent that it appears to be a caricature of the normal, while the remaining phases are either omitted entirely or are retained only in a vestigial way."

Freund noted that "troilism" (a paraphilia for observing one’s sexual/romantic partner sexually interacting with a third party, usually unbeknownst to the third party) might also be a courtship disorder, troilism being a variant of voyeurism.

Appropriate behaviors depend on the social and cultural context, including time and place. Some behaviors that are unacceptable under most circumstances, such as public nudity or sexual contact between dancers, may be accepted or even encouraged during celebrations like Carnival or Mardi Gras. Where such cultural festivals alter normative courtship behaviors, the signs of courtship disorder may be masked or altered.

Puberty usually occurs from the ages of 10 to 16 years of age and varies between boys and girls with girls normally starting earlier than boys (Shiel, Stoppler 2012). During the time of puberty is when sexual maturation starts to occur. Numerous physical changes happen during the period of puberty. Girls start to develop breasts, have growth of pubic hair and eventually begin having menstrual cycles. Boys have an enlargement of testicles and penis, growth of pubic hair, deepened voices and muscular development. Along with physical changes during puberty there are many mental changes happening. During the adolescence stage of life, boys and girls start developing thoughts related to sexual identity and start to explore and experiment with sexual behaviors. This stage of life is when sexual maturation starts to develop and one’s gender identity and sexual orientation is being developed. This is a timeframe that can possibly become confusing for the youth going through this stage of adolescence. Feelings of frustration, anxiety or depression may occur. This could be the first signs of disorder during sexual maturation.

Sexual maturity is a natural progression during the pubertal stages of adolescence. It is the timeframe where youth explore and experience sexual thoughts, situations and behaviors which ultimately lead to the identification of their gender and sexual orientation. During this timeframe abnormal feelings and thoughts can affect the progression of maturity. These abnormal occurrences would be identified as sexual maturation disorder.

Hallucinatory palinopsia consists of the following four symptom categories. A person often reports symptoms from multiple categories.

Disruption of sleep-wake cycle is almost invariably present in delirium and often predates the appearance of a full-blown episode. Minor disturbances with insomnia or excessive daytime somnolence may be hard to distinguish from other medically ill patients without delirium, but delirium typically involves more substantial alterations with sleep fragmentation or even complete sleep-wake cycle reversal that reflect disturbed circadian rhythm regulation. The relationship of circadian disturbances to the characteristic fluctuating severity of delirium symptoms over a 24-hour period or to motor disturbance is unknown.

Motor activity alterations are very common in delirium. They have been used to define clinical subtypes (hypoactive, hyperactive, mixed) though studies are inconsistent as to the prevalence of these subtypes. Cognitive impairments and EEG slowing are comparable in hyperactive and hypoactive patients though other symptoms may vary. Psychotic symptoms occur in both although the prevailing stereotype suggests that they only occur in hyperactive cases. Hypoactive cases are prone to non detection or misdiagnosis as depression. A range of studies suggest that motor subtypes differ regarding underlying pathophysiology, treatment needs, and prognosis for function and mortality though inconsistent subtype definitions and poorer detection of hypoactives impacts interpretation of these findings.

Psychotic symptoms occur in up to 50% of patients with delirium. While the common non-medical view of a delirious patient is one who is hallucinating, most people who are medically delirious do not have either hallucinations or delusions. Thought content abnormalities include suspiciousness, overvalued ideation and frank delusions. Delusions are typically poorly formed and less stereotyped than in schizophrenia or Alzheimer’s disease. They usually relate to persecutory themes of impending danger or threat in the immediate environment (e.g. being poisoned by nurses). Misperceptions include depersonalisation, delusional misidentifications, illusions and hallucinations. Hallucinations and illusions are frequently visual though can be tactile and auditory. Abnormalities of affect which may attend the state of delirium may include many distortions to perceived or communicated emotional states. Emotional states may also fluctuate, so that a delirious person may rapidly change between, for example, terror, sadness and jocularity.