An international meta-analysis over 34 jurisdictions quantified the effect size of gender as small, with most effect in Asia, lesser in Europe and Africa, and null in North America, and further finding that economic factors, internet availability, social norms and addiction-related health factors mediate the effect of gender, with nations with a greater GDP per capita having less differences in video game addiction between genders.Comorbid psychiatric disorders act as both risk factors and consequences. Indeed, there is a strong association between video game addiction and anxiety, depression, ADHD, social phobia, and poor psycho-social support. ADHD and its symptoms, such as impulsivity and conduct problems, also increase risks of developing video game disorder. Although internet gaming disorder has a strong relationship with obsessive-compulsive disorder, it is not specific and internet gaming disorder is both phenomenologically and neurobiologically distinct, which indicates that internet gaming disorder is more characterized by impulsivity than compulsivity. Familial factors appear to play an important role, although not well understood.Some personality traits, such as high neuroticism, high impulsivity, and high aggressiveness are consistently significant predictors of internet gaming disorder, and combination of personality traits seem to play a pivotal role in the acquisition, maintenance and development of the disorder. Mechanisms
Although there is much research since the 1980s on problematic online gaming use, the mechanisms are not well understood, due to inconsistent definitions used in studies. Video game structure
Some theories focus on the presumed built-in reward systems of video games, such as compulsion loops, to explain their potentially addictive nature.
It could also result from the synthesis of a cystathionase that is so greatly mutated it cannot function at all. On the other hand, vitamin B6 – responsive form still has synthesis of cystathionase. However, the cystathionase has an altered ability to bind to vitamin B6, its coenzyme. This changed interaction lowers the efficiency of cystathionase, so it cannot convert cystathionine as well. Genetics
Cystathioninuria is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome, and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.Interestingly, homozygotes and heterozygotes were able to be distinguished in one study through both plasma and urinary levels of cystathionine. The homozygote individuals had cystathionine levels greater than 0.5 moles per milligram of creatinine. Each of the homozygote individuals had a significant amount of cystathionine in the plasma as well. In contrast, the heterozygote individuals excreted approximately one tenth the amount of cystathionine as the homozygote individuals. The heterozygote individuals also had no detectable amounts of cystathionine in their plasma.The gene for cystathionase, CTH, has been sequenced and multiple mutations have been shown to be associated with the development of cystathioninuria. Two nonsense mutations were found in exon 8 and exon 11 of CTH.