The lifetime prevalence of dissociative disorders varies from 10% in the general population to 46% in psychiatric inpatients. Diagnosis can be made with the help of structured interviews such as the Dissociative Disorders Interview Schedule (DDIS) and the Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D), or with the Dissociative Experiences Scale (DES) which is a self-assessment questionnaire. Some diagnostic tests have also been adapted and/or developed for use with children and adolescents such as the Children's Version of the Response Evaluation Measure (REM-Y-71), Child Interview for Subjective Dissociative Experiences, Child Dissociative Checklist (CDC), Child Behavior Checklist (CBCL) Dissociation Subscale, and the Trauma Symptom Checklist for Children Dissociation Subscale.

There are problems with classification, diagnosis and therapeutic strategies of dissociative and conversion disorders which can be understood by the historic context of hysteria. Even current systems used to diagnose DD such as the DSM-IV and ICD-10 differ in the way the classification is determined. In most cases mental health professionals are still hesitant to diagnose patients with Dissociative Disorder, because before they are considered to be diagnosed with Dissociative Disorder these patients have more than likely been diagnosed with major depression, anxiety disorder, and most often post-traumatic disorder.

An important concern in the diagnosis of dissociative disorders is the possibility that the patient may be feigning symptoms in order to escape negative consequences. Young criminal offenders report much higher levels of dissociative disorders, such as amnesia. In one study it was found that 1% of young offenders reported complete amnesia for a violent crime, while 19% claimed partial amnesia. There have also been incidences in which people with dissociative identity disorder provide conflicting testimonies in court, depending on the personality that is present.

Dissociative disorders (DD) are widely believed to have roots in traumatic childhood experience (abuse or loss), but symptomology often goes unrecognized or is misdiagnosed in children and adolescents. There are several reasons why recognizing symptoms of dissociation in children is challenging: it may be difficult for children to describe their internal experiences; caregivers may miss signals or attempt to conceal their own abusive or neglectful behaviors; symptoms can be subtle or fleeting; disturbances of memory, mood, or concentration associated with dissociation may be misinterpreted as symptoms of other disorders.

In addition to developing diagnostic tests for children and adolescents (see above), a number of approaches have been developed to improve recognition and understanding of dissociation in children. Recent research has focused on clarifying the neurological basis of symptoms associated with dissociation by studying neurochemical, functional and structural brain abnormalities that can result from childhood trauma. Others in the field have argued that recognizing disorganized attachment (DA) in children can help alert clinicians to the possibility of dissociative disorders.

Clinicians and researchers also stress the importance of using a developmental model to understand both symptoms and the future course of DDs. In other words, symptoms of dissociation may manifest differently at different stages of child and adolescent development and individuals may be more or less susceptible to developing dissociative symptoms at different ages. Further research into the manifestation of dissociative symptoms and vulnerability throughout development is needed. Related to this developmental approach, more research is required to establish whether a young patient’s recovery will remain stable over time.

Little is known about prognosis of untreated DID. It rarely, if ever, goes away without treatment, but symptoms may resolve from time to time or wax and wane spontaneously. Patients with mainly dissociative and posttraumatic symptoms face a better prognosis than those with comorbid disorders or those still in contact with abusers, and the latter groups often face lengthier and more difficult treatment. Suicidal ideation, failed suicide attempts, and self-harm also occur. Duration of treatment can vary depending on patient goals, which can extend from elimination of all alters to merely reducing inter-alter amnesia, but generally takes years.

DID is rarely diagnosed in children, despite the average age of appearance of the first alter being three years. This fact is cited as a reason to doubt the validity of DID, and proponents of both etiologies believe that the discovery of DID in a child that had never undergone treatment would critically undermine the SCM. Conversely, if children are found to only develop DID after undergoing treatment it would challenge the traumagenic model. , approximately 250 cases of DID in children have been identified, though the data does not offer unequivocal support for either theory. While children have been diagnosed with DID before therapy, several were presented to clinicians by parents who were themselves diagnosed with DID; others were influenced by the appearance of DID in popular culture or due to a diagnosis of psychosis due to hearing voices—a symptom also found in DID. No studies have looked for children with DID in the general population, and the single study that attempted to look for children with DID not already in therapy did so by examining siblings of those already in therapy for DID. An analysis of diagnosis of children reported in scientific publications, 44 case studies of single patients were found to be evenly distributed (i.e., each case study was reported by a different author) but in articles regarding groups of patients, four researchers were responsible for the majority of the reports.

The initial theoretical description of DID was that dissociative symptoms were a means of coping with extreme stress (particularly childhood sexual and physical abuse), but this belief has been challenged by the data of multiple research studies. Proponents of the traumagenic hypothesis claim the high correlation of child sexual and physical abuse reported by adults with DID corroborates the link between trauma and DID. However, the DID-maltreatment link has been questioned for several reasons. The studies reporting the links often rely on self-report rather than independent corroborations, and these results may be worsened by selection and referral bias. Most studies of trauma and dissociation are cross-sectional rather than longitudinal, which means researchers can not attribute causation, and studies avoiding recall bias have failed to corroborate such a causal link. In addition, studies rarely control for the many disorders comorbid with DID, or family maladjustment (which is itself highly correlated with DID). The popular association of DID with childhood abuse is relatively recent, occurring only after the publication of "Sybil" in 1973. Most previous examples of "multiples" such as Chris Costner Sizemore, whose life was depicted in the book and film "The Three Faces of Eve", disclosed no history of child abuse.

Depersonalization has been described by some as a desirable state, particularly by those that have experienced it under the influence of mood-altering recreational drugs. It is an effect of dissociatives and psychedelics, as well as a possible side effect of caffeine, alcohol, amphetamine, and cannabis. It is a classic withdrawal symptom from many drugs.

Benzodiazepine dependence, which can occur with long-term use of benzodiazepines, can induce chronic depersonalization symptomatology and perceptual disturbances in some people, even in those who are taking a stable daily dosage, and it can also become a protracted feature of the benzodiazepine withdrawal syndrome.

Lieutenant Colonel Dave Grossman, in his book "", suggests that military training artificially creates depersonalization in soldiers, suppressing empathy and making it easier for them to kill other human beings.

Graham Reed (1974) noted that depersonalization occurs in relation to the experience of falling in love.

Depersonalization is also a direct symptom of Lyme disease as well as other tick-borne diseases. If depersonalization is suspected a blood-test is required in search of anti-bodies.

Depressive Disorder Not Otherwise Specified (DD-NOS) is designated by the code "311" in the DSM-IV for depressive disorders that are impairing but do not fit any of the officially specified diagnoses. According to the DSM-IV, DD-NOS encompasses "any depressive disorder that does not meet the criteria for a specific disorder." In the DSM-5, it is called unspecified depressive disorder.

Examples of disorders in this category include those sometimes described as minor depressive disorder and recurrent brief depression.

"Depression" refers to a spectrum of disturbances in mood that vary from mild to severe and from short periods to constant illness. DD-NOS is diagnosed if a patients symptoms fail to meet the criteria more common depressive disorders such as major depressive disorder or dysthymia. Although DD-NOS shares similar symptoms to dysthymia, dysthymia is classified by a period of at least 2 years of constantly recurring depressed mood, where as DD-NOS is classified by much shorter periods of depressed moods.

For most people who suffer the condition, their life will be significantly affected. DD-NOS can make many aspects of a person's daily life difficult to manage, inhibiting their ability to enjoy the things that used to make them happy. Sufferers of the disorder tend to isolate themselves from their friends and families, lose interest in some activities, and experience behavioural changes and sleeping disorders. Some sufferers also experience suicidal tendencies or suicide attempts. In addition to having these symptoms, a diagnosis of DD-NOS will only be made if the symptoms cause significant distress or impairment in social, occupational, or other important areas of functioning. For the diagnosis to be accurate, a psychiatrist is required to spend extensive time with the patient.

Symptoms of the disorder may arise due to several reasons. These include:

- Distress due to medical conditions

- Environmental effects and situations

However, the effects of drugs or medication or bereavement are not classified under the diagnosis.

A person will not be diagnosed with the condition if they have or have had any of the following: a major depressive episode, manic episode, mixed episode or hypomanic episode.

A diagnosis of the disorder will look like: "Depressive Disorder NOS 311".

It is possible for this disorder to progress over time. A patient suffering from the disorder can improve the condition with treatments. There are several types of therapies that may improve the condition, but depending on a patient’s experience of the disorder or the cause of the disorder, treatments will vary.

- Psychotherapy including behaviour therapy, Gestalt therapy, Adlerian therapy, psychoanalytic therapy and existential therapy.

- Pharmacotherapy through medications including antidepressants.

Minor depressive disorder, also known as minor depression, is a mood disorder that does not meet the full criteria for major depressive disorder but at least two depressive symptoms are present for two weeks. These symptoms can be seen in many different psychiatric and mental disorders, which can lead to more specific diagnoses of an individual's condition. However, some of the situations might not fall under specific categories listed in the "Diagnostic and Statistical Manual of Mental Disorders". Minor depressive disorder is an example of one of these nonspecific diagnoses, as it is a disorder classified in the DSM-IV-TR under the category Depressive Disorder Not Otherwise Specified (DD-NOS). The classification of NOS depressive disorders is up for debate. Minor depressive disorder as a term was never an officially accepted term, but was listed in Appendix B of the DSM-IV-TR. This is the only version of the DSM that contains the term, as the prior versions and the most recent edition, DSM-5, does not mention it.

A person is considered to have minor depressive disorder if they experience 2 to 4 depressive symptoms, with one of them being either depressed mood or loss of interest or pleasure, during a 2-week period. The person must not have experienced the symptoms for 2 years and there must not have been one specific event that caused the symptoms to arise. Although not all cases of minor depressive disorder are deemed in need of treatment, some cases are treated similarly to major depressive disorder. This treatment includes cognitive behavioral therapy (CBT), anti-depressant medication, and combination therapy. A lot of research supports the notion that minor depressive disorder is an early stage of major depressive disorder, or that it is simply highly predictive of subsequent major depressive disorder.

Treatment of minor depressive disorder has not been studied as extensively as major depressive disorder. Although there are often similarities in the treatments used, there are also differences in what may work better for the treatment of minor depressive disorder. Some third-party payers do not pay to cover treatment for minor depressive disorder.

The leading treatment techniques for minor depressive disorder are the use of antidepressants and therapy. Typically, patients with minor depression were treated by watchful waiting, prescribed antidepressants, and given brief supportive counseling, but Problem-Solving Treatment for Primary Care (PST-PC) is a Cognitive-Behavioral Therapy that has gained popularity. In one study, Problem-Solving Treatment for Primary Care (PST-PC) and Paroxetine, an antidepressant, were shown to be equally effective in significantly reducing symptoms. In another study, PST-PC was compared with the more typical care of the time and shown to reduce symptoms more quickly. Although the use of antidepressants has been widely used, not all agree that it is an appropriate treatment for some minor depression disorder settings.

Another alternative that has been researched is the use of St. John's wort ("Hypericum perforatum"). This herbal treatment has been studied by various groups with various results. Some studies show evidence of the treatment being helpful to treat minor depression, but others show that it does no better than the placebo.

It should be noticed that describing the causation of reversible dementia is extremely difficult due to the complicated biopsychological systems and the hard-to-define collection of factors associated with cognitive decline.

Roughly, the etiological factors that contribute to cognitive decline could be assigned into four categories: chemical, environmental, physical, and psychiatric. Chemical intoxication might be attributed to anesthesia, alcohol, heavy metal and commonly used medications. Jenike (1988) has recorded a certain amount of medications which may induce cognitive change in elder people.

The list is provided below.

Environmental sources include overstimulation, radical changes in lifestyle, and sensory impairment. Physical disorders which are mostly induced by the aging process, consist of thyroid and other endocrine-system deprivation; metabolic disturbance, and vitamin deficiency. Psychiatric disorders, such as chronic schizophrenia and depression could also produce cognitive decline.

In summary, the etiological factors of reversible dementia are various, subtle and frequently interactive. Therefore, in-depth medical and psychosocial evaluations are vital for accurate diagnosis and treatment design. It is important for families and patients to understand the difficulties in determining an correct diagnosis and be prepared for probable frustration and confusion during evaluation and assessment process.

Pseudosenility also reversible dementia is a condition where older people are in a state of memory loss, confusion, or disorientation that may have a cause other than the ordinary aging process. Generally, the term "reversible dementia" is used to describe most cases. A more specific term "Pseudodementia" is referring to "behavioral changes that resembler those of the progressive degenerative dementias, but which are attributable to so-called functional causes".

The "New York Times" reports that illnesses such as the flu and hydrocephalus, as well as side-effects to common medications, can produce symptoms in the elderly that are difficult to distinguish from ordinary dementia caused by aging. However, if the real cause of the effects is caught early enough, the effects can be reversed. According to studies cited in Cunha (1990), approximate 10% to 30% of patients who have exhibited symptoms of dementia might have a treatable or reversible pathologic process to some extent.

The secondary disabilities of FAS are those that arise later in life secondary to CNS damage. These disabilities often emerge over time due to a mismatch between the primary disabilities and environmental expectations; secondary disabilities can be ameliorated with early interventions and appropriate supportive services.

Six main secondary disabilities were identified in a University of Washington research study of 473 subjects diagnosed with FAS, PFAS (partial fetal alcohol syndrome), and ARND (alcohol-related neurodevelopmental disorder):

- Mental health problems: Diagnosed with ADHD, Clinical Depression, or other mental illness, experienced by over 90% of the subjects

- Disrupted school experience: Suspended or expelled from school or dropped out of school, experienced by 60% of the subjects (age 12 and older)

- Trouble with the law: Charged or convicted with a crime, experienced by 60% of the subjects (age 12 and older)

- Confinement: For inpatient psychiatric care, inpatient chemical dependency care, or incarcerated for a crime, experienced by about 50% of the subjects (age 12 and older)

- Inappropriate sexual behavior: Sexual advances, sexual touching, or promiscuity, experienced by about 50% of the subjects (age 12 and older)

- Alcohol and drug problems: Abuse or dependency, experienced by 35% of the subjects (age 12 and older)

Two additional secondary disabilities exist for adults:

- Dependent living: Group home, living with family or friends, or some sort of assisted living, experienced by 80% of the subjects (age 21 and older)

- Problems with employment: Required ongoing job training or coaching, could not keep a job, unemployed, experienced by 80% of the subjects (age 21 and older)

Amount, frequency, and timing of prenatal alcohol use can dramatically impact the other three key features of FASD. While consensus exists that alcohol is a teratogen, there is no clear consensus as to what level of exposure is toxic. The CDC guidelines are silent on these elements diagnostically. The IOM and Canadian guidelines explore this further, acknowledging the importance of significant alcohol exposure from regular or heavy episodic alcohol consumption in determining, but offer no standard for diagnosis. Canadian guidelines discuss this lack of clarity and parenthetically point out that "heavy alcohol use" is defined by the National Institute on Alcohol Abuse and Alcoholism as five or more drinks per episode on five or more days during a 30-day period.

"The 4-Digit Diagnostic Code" ranking system distinguishes between levels of prenatal alcohol exposure as "high risk" and "some risk". It operationalizes high risk exposure as a blood alcohol concentration (BAC) greater than 100 mg/dL delivered at least weekly in early pregnancy. This BAC level is typically reached by a 55 kg female drinking six to eight beers in one sitting.

Although many perinatal and prenatal risk factors for ONH have been suggested, the predominant, enduring, most frequent risk factors are young maternal age and primiparity (the affected child being the first child born to the mother). Increased frequency of delivery by caesarean section and fetal/neonatal complications, preterm labor, gestational vaginal bleeding, low maternal weight gain, and weight loss during pregnancy are also associated with ONH.

Optic nerve hypoplasia (ONH) is a congenital condition in which the optic nerve is underdeveloped (small).

Many times, de Morsier’s Syndrome or septo-optic dysplasia (SOD) is associated with ONH, however, it is possible to have ONH without any additional issues like SOD. SOD is a condition that can involve multiple problems in the midline structures of the brain, stemming from miswiring of the brain and central nervous system. Besides having small optic nerves, persons with ONH can have agenesis of the corpus callosum, absence of the septum pellucidum, maldevelopment of the anterior and posterior pituitary gland, and anomalies of the hypothalamus. Because of this, all children with ONH are at risk for developmental delays and hormonal deficiencies, regardless of severity of ONH, or whether abnormalities are visible by MRI.

ONH is the single leading cause of permanent legal blindness in children in the western world. The incidence of ONH is increasing, although it is difficult to estimate the true prevalence. Between 1980 and 1999, the occurrences of ONH in Sweden increased four-fold to 7.2 per 100,000, while all other causes of childhood blindness had declined. In 1997, ONH overtook retinopathy of prematurity as the single leading cause of infant blindness in Sweden, with 6.3 in every 100,000 births diagnosed with ONH. The most recent prevalence report out of England in 2006 is 10.9 per 100,000.

Male gender, proteinuria (especially > 2 g/day), hypertension, smoking, hyperlipidemia, older age, familial disease and elevated creatinine concentrations are markers of a poor outcome. Frank hematuria has shown discordant results with most studies showing a better prognosis, perhaps related to the early diagnosis, except for one group which reported a poorer prognosis. Proteinuria and hypertension are the most powerful prognostic factors in this group.

There are certain other features on kidney biopsy such as interstitial scarring which are associated with a poor prognosis. ACE gene polymorphism has been recently shown to have an impact with the DD genotype associated more commonly with progression to kidney failure.

Dentin dysplasia (DD) is a rare genetic developmental disorder dentine production of the teeth, commonly exhibiting an autosomal dominant inheritance that causes malformation of the root. It affects both primary and permanent dentitions in approximately 1 in every 100,000 patients. It is characterized by presence of normal enamel but atypical dentin with abnormal pulpal morphology. Witkop in 1972 classified DD into two types which are Type I (DD-1) is the radicular type, and type II (DD-2) is the coronal type. DD-1 has been further divided into 4 different subtypes (DD-1a,1b,1c,1d) based on the radiographic features.

The mutation in collagen type 1 (COL1 A1, COL1 A2) causes DI-1. It is similar to the systemic condition dental features known as osteogenesis imperfect. DI-2, DI-3 and DD-2 share the same genetic mutation of dentin sialophosphoprotein, that is located on chromosome 4. They are autosomal-dominant diseases with complete penetrance and variable expressivity. Due to the same genetic mutation, these diseases would often result in overlapping clinical and radiographic features. Therefore, prevailing theories suggests that DI-2, DI-3 and DD-2 are categorized as a single disease entity with variable severity of expression. However, the causes of DD-1 have yet to be theorized.

Men are affected three times as often as women. There is also marked geographic variation in the prevalence of IgA nephropathy throughout the world. It is the most common glomerular disease in the Far East and Southeast Asia, accounting for almost half of all the patients with glomerular disease. However, it accounts for only about 25% of the proportion in European and about 10% among North Americans, with African–Americans having a very low prevalence of about 2%. However, a confounding factor in this analysis is the existing policy of screening and use of kidney biopsy as an investigative tool. School children in Japan undergo routine urinalysis (as do army recruits in Singapore) and any suspicious abnormality is pursued with a kidney biopsy, which might partly explain the high observed incidence of IgA nephropathy in those countries.

While the number of penicillin-resistant bacteria is increasing, penicillin can still be used to treat a wide range of infections caused by certain susceptible bacteria, including Streptococci, Staphylococci, Clostridium, and Listeria genera. The following list illustrates minimum inhibitory concentration susceptibility data for a few medically significant bacteria:

- "Listeria monocytogenes": from less than or equal to 0.06 μg/ml to 0.25 μg/ml

- "Neisseria meningitidis": from less than or equal to 0.03 μg/ml to 0.5 μg/ml

- "Staphylococcus aureus": from less than or equal to 0.015 μg/ml to more than 32 μg/ml

Common (≥ 1% of people) adverse drug reactions associated with use of the penicillins include diarrhoea, hypersensitivity, nausea, rash, neurotoxicity, urticaria, and superinfection (including candidiasis). Infrequent adverse effects (0.1–1% of people) include fever, vomiting, erythema, dermatitis, angioedema, seizures (especially in people with epilepsy), and pseudomembranous colitis. Penicillin can also induce serum sickness or a serum sickness-like reaction in some individuals. Serum sickness is a type III hypersensitivity reaction that occurs one to three weeks after exposure to drugs including penicillin. It is not a true drug allergy, because allergies are type I hypersensitivity reactions, but repeated exposure to the offending agent can result in an anaphylactic reaction. Anaphylaxis will occur in approximately 0.01% of patients.

Pain and inflammation at the injection site is also common for parenterally administered benzathine benzylpenicillin, benzylpenicillin, and, to a lesser extent, procaine benzylpenicillin.