title: Association of Per3 length polymorphism with bipolar I disorder and schizophrenia.
abstract: BACKGROUND
  Sleep-wake disturbances have frequently been reported in bipolar disorder and schizophrenia, and are considered to be caused by an underlying circadian rhythm disorder. The study presented here was designed to investigate the existence of Per3 polymorphism in bipolar disorder type I (BD-I) and schizophrenic patients in South India.
  
  
  METHODS
  Blood samples were collected from 311 BD-I patients, 293 schizophrenia patients, and 346 age- and sex-matched normal controls. Per3 genotyping was performed on DNA by polymerase chain reaction using specific primers.
  
  
  RESULTS
  An increased prevalence of five repeat homozygotes was seen in BD-I patients as compared with healthy controls (odds ratio =1.72 [95% confidence interval: 1.08-2.76, P=0.02]). In BD-I patients, the frequency of the five repeat allele was higher (allele frequency =0.41), and that of the four repeat allele lower (allele frequency =0.36) (χ (2)=4.634; P<0.03) than in the control group. No significant association was observed in the allele frequencies of four and five repeat alleles in schizophrenia patients when compared with controls.
  
  
  CONCLUSIONS
  The occurrence of the five repeat allele of Per3 may be a risk factor for BD-I onset in this ethnic group.
authors.affiliation: Department of Animal Behaviour and Physiology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India.
authors.forename: Ramanujam
authors.initials: R
authors.lastname: Karthikeyan
authors.affiliation: Department of Animal Behaviour and Physiology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India.
authors.forename: Ganapathy
authors.initials: G
authors.lastname: Marimuthu
authors.affiliation: MS Chellamuthu Trust and Research Foundation, KK Nagar, Madurai, India.
authors.forename: Chellamuthu
authors.initials: C
authors.lastname: Ramasubramanian
authors.affiliation: MS Chellamuthu Trust and Research Foundation, KK Nagar, Madurai, India.
authors.forename: Gautham
authors.initials: G
authors.lastname: Arunachal
authors.affiliation: University Sleep Disorders Center, College of Medicine, National Plan for Science and Technology, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Ahmed S
authors.initials: AS
authors.lastname: BaHammam
authors.affiliation: Independent researcher, Toronto, Ontario, Canada.
authors.forename: David Warren
authors.initials: DW
authors.lastname: Spence
authors.affiliation: Department of Teaching and Research, Faculty of Medical Sciences, Pontificia Universidad Católica Argentina, Buenos Aires, Argentina.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Cardinali
authors.affiliation: Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Brown
authors.affiliation: Center for Healthful Behavior Change (CHBC), Division of Health and Behavior, Department of Population Health, NYU Langone Medical Center, Clinical and Translational Research Institute, New York, New York, USA.
authors.forename: Seithikurippu R
authors.initials: SR
authors.lastname: Pandi-Perumal
keywords: Per3 polymorphism; bipolar disorder; circadian rhythms; clock genes; schizophrenia