Further evidence linking streptococcal infections to neuropsychiatric disorders

Researchers have added to the body of evidence linking streptococcal infection to the onset or exacerbation of several neuropsychiatric disorders. Studies have suggested a link between group A b -haemolytic streptococcal (GABHS) infections with the prepubescent onset of obsessive-compulsive disorder (OCD), Tourette syndrome (TS) and tic disorder; however, most of these studies have involved small samples or are based on case reports. Only one large-scale study has been conducted to date which found that patients with new onset OCD, TS or tic disorder were significantly more likely to have had streptococcal infections in the year preceding the onset of the psychiatric illness. Leslie et al. sought to replicate this study using a larger, more nationally representative US sample. They used health insurance claims data to compare the occurrence of streptococcal infection in a sample of privately insured children aged 4—13 years in the year prior to a diagnosis of OCD, TS, tic disorder, attention-deficit/hyperactivity disorder (ADHD), or major depressive disorder (MDD) to that of matched controls. Logistic regression modelling was used to determine the association of prior streptococcal infection of the throat (‘strep throat’) or scarlet fever with a diagnosis of OCD, TS or tic disorder. The investigation was repeated for infectious diseases otitis media and sinusitis as well as one non-infections condition (migraine). They identified 742 cases of newly diagnosed OCD, TS and tic disorder along with 3,647 controls. Analyses revealed that compared with controls, patients diagnosed with the aforementioned neuropsychiatric disorders were more likely to have had a diagnosis of streptococcal infection in the year preceding diagnosis (odds ratio [OR] 1.54). Furthermore, prior streptococcal infection was also associated with incident diagnoses of ADHD (OR 1.20) and MDD (OR 1.63) among samples of 3,650 cases of newly diagnosed ADHD (18,114 controls), and 341 cases of newly diagnosed MDD (1,710 controls), respectively. No increased occurrence of otitis media or migraine was found before the initial diagnoses of OCD, tic disorders and TS; however, an increased prior occurrence of sinusitis was observed (OR 1.40). “Although we hesitate to read much into this finding, we cannot discount the possibility that it may reflect an increased susceptibility to some but not all infectious diseases in children with these neuropsychiatric disorders and/or the possibility that infection with agents other than GABHS may predispose to this class of disorders,” they stated. The authors acknowledged that genetic factors have been implicated in the development of TS, OCD, ADHD and paediatric MDD, stating that infection may serve as a trigger for symptoms in only a subset of genetically susceptible individuals. “It is likely that the aetiology and genetics of these disorders are complex, such that antecedent infections are a causal agent in only a subset of cases,” they stated. The authors concluded that their results add to the body of evidence suggesting that an association between streptococcal infections and several neuropsychiatric disorders including OCD, TS, tic disorder, ADHD, and MDD does exist. Reference Leslie, D. Kozma, L. et al. 2008, ‘neuropsychiatric disorders associated with streptococcal infection: A case-control study among privately insured children’ Journal of the AmericanAcademy of Child and Adolescent Psychiatry 47: DOI:10.1097/CHI.013e3181825a3d....