Early onset dementia is dementia in which symptoms first appear before the age of 65. The term favored until about 2000 was presenile dementia; young onset dementia is also used.Early onset dementia may be caused by degenerative or vascular disease, or it may be due to other causes, such as alcohol-related dementia and other inflammatory or infectious processes. Early-onset Alzheimers disease, vascular dementia and frontotemporal lobar degeneration are the most common forms of early onset dementia, with Alzheimers accounting for between 30 and 40%. Early onset dementia may also occur, less frequently, in the Lewy body dementias (dementia with Lewy bodies and Parkinsons disease dementia), multiple sclerosis, Huntingtons disease and other conditions. References
Further reading
Collins JD, Henley SM, Suárez-González A (July 2020). "A systematic review of the prevalence of depression, anxiety, and apathy in frontotemporal dementia, atypical and young-onset Alzheimers disease, and inherited dementia". Int Psychogeriatr (Review): 1–20. doi:10.1017/S1041610220001118. PMID 32684177. S2CID 220653830. Ducharme S, Dols A, Laforce R,  et al. (June 2020). "Recommendations to distinguish behavioural variant frontotemporal dementia from psychiatric disorders". Brain (Review). 143 (6): 1632–1650. doi:10.1093/brain/awaa018. PMC 7849953. PMID 32129844. Nwadiugwu M (September 2021). "Early-onset dementia: key issues using a relationship-centred care approach". Postgrad Med J (Review). 97 (1151): 598–604. doi:10.1136/postgradmedj-2020-138517. PMC 8408578. PMID 32883770. Roman de Mettelinge T, Calders P, Cambier D (2021). "The Effects of Aerobic Exercise in Patients with Early-Onset Dementia: A Scoping Review". Dement Geriatr Cogn Disord (Review). 50 (1): 9–16. doi:10.1159/000516231. PMID 33957623. S2CID 233983643.
Despite inconsistencies in the types of abnormalities found, evidence points towards dysfunction of serotonergic systems in OCD. Orbitofrontal cortex overactivity is attenuated in people who have successfully responded to SSRI medication, a result believed to be caused by increased stimulation of serotonin receptors 5-HT2A and 5-HT2C.A complex relationship between dopamine and OCD has been observed. Although antipsychotics, which act by antagonizing dopamine receptors, may improve some cases of OCD, they frequently exacerbate others. Antipsychotics, in the low doses used to treat OCD, may actually increase the release of dopamine in the prefrontal cortex, through inhibiting autoreceptors. Further complicating things is the efficacy of amphetamines, decreased dopamine transporter activity observed in OCD, and low levels of D2 binding in the striatum. Furthermore, increased dopamine release in the nucleus accumbens after deep brain stimulation correlates with improvement in symptoms, pointing to reduced dopamine release in the striatum playing a role in generating symptoms.Abnormalities in glutamatergic neurotransmission have implicated in OCD. Findings such as increased cerebrospinal glutamate, less consistent abnormalities observed in neuroimaging studies, and the efficacy of some glutamatergic drugs (such as the glutamate-inhibiting riluzole) have implicated glutamate in OCD. OCD has been associated with reduced N-Acetylaspartic acid in the mPFC, which is thought to reflect neuron density or functionality, although the exact interpretation has not been established. Diagnosis
Formal diagnosis may be performed by a psychologist, psychiatrist, clinical social worker, or other licensed mental health professional. OCD, like other mental and behavioral health disorders, cannot be diagnosed by a medical exam.