Because the internet and the media contribute to furthering shared delusions, DP has also been called folie à Internet; when affected people are separated, their symptoms typically subside, but most still require treatment.Approximately eight out of ten individuals with DP have co-occurring conditions—mainly depression, followed by substance abuse and anxiety; their personal and professional lives are frequently disrupted as they are extremely distressed about their symptoms.A 2011 Mayo Clinic study of 108 patients failed to find evidence of skin infestation in skin biopsies and patient-provided specimens; the study concluded that the feeling of skin infestation was DP. Cause
The cause of delusional parasitosis is unknown. It may be related to excess dopamine in the brains striatum, resulting from diminished dopamine transporter (DAT) function, which regulates dopamine reuptake in the brain. Evidence supporting the dopamine theory is that medications that inhibit dopamine reuptake (for example cocaine and amphetamines) are known to induce symptoms such as formication. Other conditions that also demonstrate reduced DAT functioning are known to cause secondary DP; these conditions include "schizophrenia, depression, traumatic brain injury, alcoholism, Parkinsons and Huntingtons diseases, human immunodeficiency virus infection, and iron deficiency". Further evidence is that antipsychotics improve DP symptoms, which may be because they affect dopamine transmission.
Diagnosis
Delusional parasitosis is diagnosed when the delusion is the only symptom of psychosis, the delusion has lasted a month or longer, behavior is otherwise not markedly odd or impaired, mood disorders—if present at any time—have been comparatively brief, and the delusion cannot be better explained by another medical condition, mental disorder, or the effects of a substance. For diagnosis, the individual must attribute abnormal skin sensations to the belief that they have an infestation, and be convinced that they have an infestation even when evidence shows they do not.The condition is recognized in two forms: primary and secondary. In primary delusional parasitosis, the delusions are the only manifestation of a psychiatric disorder. Secondary delusional parasitosis occurs when another psychiatric condition, medical illness or substance (medical or recreational) use causes the symptoms; in these cases, the delusion is a symptom of another condition rather than the disorder itself. Secondary forms of DP can be functional (due to mainly psychiatric disorders) or organic (due to other medical illness or organic disease. The secondary organic form may be related to vitamin B12 deficiency, hypothyroidism, anemia, hepatitis, diabetes, HIV/AIDS, syphilis, or abuse of cocaine.Examination to rule out other causes is key to diagnosis. Parasitic infestations are ruled out via skin examination and laboratory analyses. Bacterial infections may be present as a result of the individual constantly manipulating their skin. Other conditions that can cause itching skin are also ruled out; this includes a review of medications that may lead to similar symptoms.