Objectives: Psychiatric symptoms and disorders are commonly reported with
epilepsy. This study aimed to determine the prevalence of interictal
psychosis (IIP) in adults with
epilepsy and its risk predictors. Methods: The study included 710 patients (mean age: 36.40 years; age at onset: 13.58 years; duration of
epilepsy: 22.80 years). All underwent neurological and psychiatric interviewing, electroencephalography and brain imaging. Results: IIP was reported in 20.65%, of them 50% had
temporal lobe epilepsy with impaired awareness and/or to bilateral tonic clonic, 42.47% had
frontal lobe epilepsy with impaired awareness and/or to bilateral tonic clonic and 7.53% had
generalized tonic-clonic seizures. Compared to patients without
psychosis, patients with
psychosis were older at age of examination, had earlier age at onset, frequent
seizures, longer duration of
epilepsy and long-term
antiepileptic drugs therapy and many relatives with
epilepsy. Nearly 76.71% had history of postictal
psychosis (PIP). The mean age of onset of IIP was 30.45 years and its mean duration was 3.84 months. Approximately 22% of patients with IIP had family history of
psychosis. Patients developed IIP 10 years or more after
epilepsy onset. Multivariate logistic regression analyses showed that predictors for IIP were the age at onset and duration of
epilepsy, number of
seizures, family history of
epilepsy or
psychosis, history of PIP and different types of
epilepsy. Conclusion: IIP is not infrequent with chronic
epilepsy regardless to its type. These findings emphasize the importance of optimizing patients' treatment and early recognition and management of IIP. Abbreviations: IIP: interictal
psychosis; PIP: post-ictal
psychosis; TLE:
temporal lobe epilepsy; FLE:
frontal lobe epilepsy; GTC: generalized tonic clonic; AEDs:
antiepileptic drugs; CBZ:
carbamazepine; VPA:
valproate; LEV:
levetiracetam; APDs:
antipsychotic drugs.