title: The incidence and prevalence of psychiatric disorders in multiple sclerosis: a systematic review.
abstract: BACKGROUND
  Psychiatric comorbidity is associated with lower quality of life, more fatigue, and reduced adherence to disease-modifying therapy in multiple sclerosis (MS).
  
  
  OBJECTIVE
  The objectives of this review are to estimate the incidence and prevalence of selected comorbid psychiatric disorders in MS and evaluate the quality of included studies.
  
  
  METHODS
  We searched the PubMed, PsychInfo, SCOPUS, and Web of Knowledge databases and reference lists of retrieved articles. Abstracts were screened for relevance by two independent reviewers, followed by full-text review. Data were abstracted by one reviewer, and verified by a second reviewer. Study quality was evaluated using a standardized tool. For population-based studies we assessed heterogeneity quantitatively using the I² statistic, and conducted meta-analyses.
  
  
  RESULTS
  We included 118 studies in this review. Among population-based studies, the prevalence of anxiety was 21.9% (95% CI: 8.76%-35.0%), while it was 14.8% for alcohol abuse, 5.83% for bipolar disorder, 23.7% (95% CI: 17.4%-30.0%) for depression, 2.5% for substance abuse, and 4.3% (95% CI: 0%-10.3%) for psychosis.
  
  
  CONCLUSIONS
  This review confirms that psychiatric comorbidity, particularly depression and anxiety, is common in MS. However, the incidence of psychiatric comorbidity remains understudied. Future comparisons across studies would be enhanced by developing a consistent approach to measuring psychiatric comorbidity, and reporting of age-, sex-, and ethnicity-specific estimates.
authors.affiliation: Department of Internal Medicine, University of Manitoba, Canada/Department of Community Health Sciences, University of Manitoba, Canada rmarrie@hsc.mb.ca.
authors.forename: Ruth Ann
authors.initials: RA
authors.lastname: Marrie
authors.affiliation: Scientific and Clinical Review Associates, LLC, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Reingold
authors.affiliation: Mellen Center for MS Treatment and Research, Cleveland Clinic, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Cohen
authors.affiliation: Department of Neurology and Neurotherapeutics, University of Texas Southwestern, USA.
authors.forename: Olaf
authors.initials: O
authors.lastname: Stuve
authors.affiliation: Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Trojano
authors.affiliation: Department of Neurology, Copenhagen University Hospital Rigshospitalet, Denmark.
authors.forename: Per Soelberg
authors.initials: PS
authors.lastname: Sorensen
authors.affiliation: Department of Biostatistics, University of Alabama at Birmingham, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Cutter
authors.affiliation: Department of Community Health Sciences, University of Manitoba, Canada.
authors.forename: Nadia
authors.initials: N
authors.lastname: Reider
mesh_terms: D015897:Comorbidity; D006801:Humans; D015994:Incidence; D001523:Mental Disorders / Q000453:epidemiology*; D009103:Multiple Sclerosis / Q000453:epidemiology*; D015995:Prevalence
keywords: Multiple sclerosis; anxiety; bipolar disorder; comorbidity; depression; incidence; prevalence; psychosis; systematic review