A wide range of factors have been identified as being predictive of PCS, including low socioeconomic status, previous mTBI, a serious associated injury, headaches, an ongoing court case, and female gender. Being older than 40 and being female have also been identified as being predictive of a diagnosis of PCS, and women tend to report more severe symptoms. In addition, the development of PCS can be predicted by having a history of alcohol abuse, low cognitive abilities before the injury, a personality disorder, or a medical illness not related to the injury. PCS is also more prevalent in people with a history of psychiatric conditions such as clinical depression or anxiety before the injury.

Mild brain injury-related factors that increase the risk for persisting post-concussion symptoms include an injury associated with acute headache, dizziness, or nausea; an acute Glasgow Coma Score of 13 or 14; and suffering another head injury before recovering from the first. The risk for developing PCS also appears to be increased in people who have traumatic memories of the injury or expect to be disabled by the injury.

It is not known exactly how common PCS is. Estimates of the prevalence at 3 months post-injury are between 24 and 84%, a variation possibly caused by different populations or study methodologies. The estimated incidence of PPCS (persistent postconcussive syndrome) is around 10% of mTBI cases. Since PCS by definition only exists in people who have suffered a head injury, demographics and risk factors are similar to those for head injury; for example, young adults are at higher risk than others for receiving head injury, and, consequently, of developing PCS.

The existence of PCS in children is controversial. It is possible that children's brains have enough plasticity that they are not affected by long-term consequences of concussion (though such consequences are known to result from moderate and severe head trauma). On the other hand, children's brains may be more vulnerable to the injury, since they are still developing and have fewer skills that can compensate for deficits. Clinical research has found higher rates of post-concussion symptoms in children with TBI than in those with injuries to other parts of the body, and that the symptoms are more common in anxious children. Symptoms in children are similar to those in adults, but children exhibit fewer of them. Evidence from clinical studies found that high school-aged athletes had slower recoveries from concussion as measured by neuropsychological tests than college-aged ones and adults. PCS is rare in young children.

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease found in people who have had multiple head injuries. Symptoms may include behavioral problems, mood problems, and problems with thinking. This typically does not begin until years after the injuries. It often gets worse over time and can result in dementia. It is unclear if the risk of suicide is altered.

Most documented cases have occurred in athletes involved in contact sports such as football, wrestling, ice hockey, and soccer. Other risk factors include being in the military, prior domestic violence, and repeated banging of the head. The exact amount of trauma required for the condition to occur is unknown. Definitive diagnosis can only occur at autopsy. It is a form of tauopathy.

As of 2017 there is no specific treatment. Rates of disease have been found to be about 30% among those with a history of multiple head injuries. Population rates, however, are unclear. Research into brain damage as a result of repeated head injuries began in the 1920s, at which time the condition was known as "punch drunk". Changing the rules in some sports has been discussed as a means of prevention.

Symptoms of CTE, which occur in four stages, generally appear 8 to 10 years after an athlete experiences repetitive mild traumatic brain injury.

First-stage symptoms include attention deficit hyperactivity disorder as well as confusion, disorientation, dizziness, and headaches. Second-stage symptoms include memory loss, social instability, impulsive behavior, and poor judgment. Third and fourth stages include progressive dementia, movement disorders, hypomimia, speech impediments, sensory processing disorder, tremors, vertigo, deafness, depression and suicidality.

Additional symptoms include dysarthria, dysphagia, cognitive disorder such as amnesia, and ocular abnormalities, such as ptosis.

The condition manifests as dementia, or declining mental ability, problems with memory, dizzy spells or lack of balance to the point of not being able to walk under one's own power for a short time and/or Parkinsonism, or tremors and lack of coordination. It can also cause speech problems and an unsteady gait. Patients with DP may be prone to inappropriate or explosive behavior and may display pathological jealousy or paranoia.

Roberts syndrome is an extremely rare condition that only affects about 150 reported individuals. Although there have been only about 150 reported cases, the affected group is quite diverse and spread worldwide. Parental consanguinity (parents are closely related) is common with this genetic disorder. The frequency of Roberts syndrome carriers is unknown.

Roberts syndrome, or sometimes called "pseudothalidomide syndrome", is an extremely rare genetic disorder that is characterized by mild to severe prenatal retardation or disruption of cell division, leading to malformation of the bones in the skull, face, arms, and legs.

Roberts syndrome is also known by many other names, including: hypomelia-hypotrichosis-facial hemangioma syndrome, SC syndrome (once thought to be an entirely separate disease), pseudothalidomide syndrome, Roberts-SC phocomelia syndrome, SC phocomelia syndrome, Appelt-Gerken-Lenz syndrome, RBS, SC pseudothalidomide syndrome, and tetraphocomelia-cleft palate syndrome. It is a genetic disorder caused by the mutation of the ESCO2 gene on 8th chromosome. Named after the famous Philadelphia surgeon and physician, Dr. John Bingham Roberts (1852–1924), who first described the syndrome in 1919, it is one of the rarest autosomal recessive disorders, affecting approximately 150 known individuals.

The syndrome is both autosomal, in that there are equal numbers of copies of the gene in both males and females, and recessive, meaning the child must inherit the defective gene from both parents. The mutation causes cell division to occur slowly or unevenly, and the cells with abnormal genetic content die. Roberts syndrome can affect both males and females. Although the disorder is rare, the affected group is diverse. The mortality rate is high in severely affected individuals.

Computer addiction can be described as the excessive or compulsive use of the computer which persists despite serious negative consequences for personal, social, or occupational function. Another clear conceptualization is made by Block, who stated that "Conceptually, the diagnosis is a compulsive-impulsive spectrum disorder that involves online and/or offline computer usage and consists of at least three subtypes: excessive gaming, sexual preoccupations, and e-mail/text messaging". While it was expected that this new type of addiction would find a place under the compulsive disorders in the DSM-5, the current edition of the "Diagnostic and Statistical Manual of Mental Disorders", it is still counted as an unofficial disorder. The concept of computer addiction is broadly divided into two types, namely offline computer addiction and online computer addiction. The term offline computer addiction is normally used when speaking about excessive gaming behavior, which can be practiced both offline and online. Online computer addiction, also known as Internet addiction, gets more attention in general from scientific research than offline computer addiction, mainly because most cases of computer addiction are related to the excessive use of the Internet.

Although addiction is usually used to describe dependence on substances, addiction can also be used to describe pathological Internet use. Experts on Internet addiction have described this syndrome as an individual being intensely working on the Internet, prolonged use of the Internet, uncontrollable use of the Internet, unable to use the Internet with efficient time, not being interested in the outside world, not spending time with people from the outside world, and an increase in their loneliness and dejection. However, simply working long hours on the computer does not necessarily mean someone is addicted.

Kimberly Young indicates that previous research links internet/computer addiction with existing mental health issues, most notably depression. She states that computer addiction has significant effects socially such as low self-esteem, psychologically and occupationally which led many subjects to academic failure.

According to a Korean study on internet/computer addiction, pathological use of the internet results in negative life impacts such as job loss, marriage breakdown, financial debt, and academic failure. 70% of internet users in Korea are reported to play online games, 18% of which are diagnosed as game addicts which relates to internet/computer addiction. The authors of the article conducted a study using Kimberly Young's questionnaire. The study showed that the majority of those who met the requirements of internet/computer addiction suffered from interpersonal difficulties and stress and that those addicted to online games specifically responded that they hoped to avoid reality.

Biliary microlithiasis refers to the creation of small gallstones less than 3mm in diameter in the biliary duct or gallbladder.

It has been suggested as a cause of postcholecystectomy syndrome, or PCS, the symptoms of which include:

- Upset stomach, nausea, and vomiting.

- Gas, bloating, and diarrhea.

- Persistent pain in the upper right abdomen.