The presence of a single first-rank auditory hallucination (FRAH) or bizarre delusion (BD) is sufficient to satisfy the symptom criterion for a DSM-IV-TR diagnosis of schizophrenia. We queried two independent databases to investigate how prevalent FRAH and BD are in schizophrenia spectrum disorders and whether the diagnosis depends on them. FRAH was common in both datasets (42.2% and 55.2%) and...

Although delusions are prima facie evidence of psychosis, their mere presence is not a sufficient condition for exculpation on the grounds of insanity. In most cases, a determination of insanity will depend on the specific content of the delusions and whether, as a result of these delusions, the defendant was unable to know or appreciate the wrongfulness of his or her act. Delusions may be subd...

Four schizophrenic patients with paranoid and grandiose delusions who had been hospitalized for an average of 17 yr were exposed to social reinforcement contingencies in a multiple baseline design. During the baseline period, each patient was interviewed for four 10-min sessions each day. The elapsed time from onset of conversation to onset of delusional talk was recorded. At the end of each da...

A patient with delusion of pregnancy as an early feature of frontotemporal dementia with motor neurone disease (FTD/MND) who was reported some years ago was posthumously found to harbor the C9ORF72 hexanucleotide repeat expansion, now known to be the most common genetic cause of FTD/MND. Some series have found psychosis to be common in FTD associated with this mutation, so this test should be c...

The authors report a case of a 68-year-old man with an unrecognized insulinoma manifesting with neuropsychiatric symptoms. For two years, he presented with unspecified behavior changes, autonomic and neuroglycopenic symptoms, which led him to be misdiagnosed with a neurologic and psychiatric disorder before the insulinoma was recognized. Following neurological alterations in context of hypoglyc...

Delusions of parasitosis manifest in the patient's firm belief that he or she has pruritus due to an infestation with insects. Patients may present with clothing lint, pieces of skin, or other debris contained in plastic wrap, on adhesive tape, or in matchboxes. They typically state that these contain the parasites; however, these collections have no insects or parasites. This presentation is c...

Although the practice of infectious diseases involves a broad range of surgical and medical disciplines, interactions with psychiatry are infrequent. Delusional infestation is a condition where an individual has a firmly fixed false belief that they have an infection. Delusional infestation challenges the infectious diseases specialist who must diligently rule out the presence of a true infecti...

Delusions are defined as irrational beliefs that compromise good functioning. However, in the empirical literature, delusions have been found to have some psychological benefits. One proposal is that some delusions defuse negative emotions and protect one from low self-esteem by allowing motivational influences on belief formation. In this paper I focus on delusions that have been construed as ...