Study Report

Reference	Selch, S., 2007 PMID: 17210142
Citation	Selch, S., A. Strobel, et al. (2007). "MLC1 polymorphisms are specifically associated with periodic catatonia, a subgroup of chronic schizophrenia." Biol Psychiatry 61(10): 1211-1214.
Disease Type	Bipolar Disorder & Schizophrenia
Study Design	case-control
Study Type	Candidate-gene association study
Sample Size	212 chronic schizophrenic patients, 106 bipolar patients and 284 controls
SNP/Region/Marker Size	4 SNPs
Predominant Ethnicity	Caucasian
Population	Germany

Sample Diagnosis	ICD-10 and Leonhard (1999) diagnosis system
Sample Status	A total of 318 unrelated patients from Lower Franconia participated. Two hundred-twelve patients suffered from chronic, nonremitting schizophrenic disorders according to ICD-10. A further 106 inpatients suffered from bipolar affective disorder (BPD). Only patients with at least one manic and one depressive episode leading to treatment were included. According to the Leonhard (1999) classification system, 61 patients suffered from affect-laden paraphrenia, 56 suffered from PC, and 39 suffered from cataphasia, i.e., 156 suffered from type A schizophrenia (Reif et al. 2006). Fifty-five suffered from type B schizophrenia, and manic-depressive illness was present in 107 patients.
Technique	genotyping using standard PCR and subsequent restriction enzyme digest followed by gel electrophoresis
Statistical Method	Single association tests were performed by means of chi-square tests using SPSS. In addition to tests using the full genotype, they performed tests using dichotomized genotypes by grouping together carriers of one or two copies of the rare alleles of each marker. Power calculations using GPOWER indicated that for the dichotomous genotype tests, the power to detect a small effect was .61/.51/.45 for the comparisons SCZ/BPD/PC versus control subjects, whereas the power to detect a medium effect was for 1.0 for all comparisons. Haplotype association tests were performed using GENECOUNTING.
Result Summary	Both intronic and promoter polymorphisms were specifically and significantly associated with periodic catatonia but not schizophrenia or bipolar disorder in general. A haplotype constructed from all polymorphisms was also associated with periodic catatonia. The MLC1 variation is associated with periodic catatonia; whether it constitutes a susceptibility or a modifier gene has to be determined.