title: Perceived Risk Modifies the Effect of HIV Knowledge on Sexual Risk Behaviors.
abstract: BACKGROUND
  There is a large controversy in the literature about the inter-relations between perceived risk, knowledge, and risk behavior in different settings, and people at HIV risk are not an exception.
  
  
  OBJECTIVE
  To assess additive and multiplicative effect of perceived HIV risk and HIV knowledge on sexual risk behavior of Injecting Drug Users (IDUs).
  
  
  METHODS
  We enrolled 162 street based IDUs to this analysis. Data came from a national survey of IDUs in Iran, with a cross sectional design. Socio-demographics (employment, education, marital status), HIV knowledge, perceived HIV risk, and four different sexual risk behavior were registered. In the first step, using spearman test, the association of HIV knowledge and risk behavior were tested, then possible moderating effect of perceived HIV risk on this association was determined.
  
  
  RESULTS
  Although among IDUs with low perceived HIV risk, HIV knowledge was negatively associated with sexual risk behavior (P < 0.05 for all), this association was not significant among IDUs with high perceived HIV risk (P > 0.05 for all). Thus perceived HIV risk moderated the association between HIV knowledge and sexual risk behavior.
  
  
  CONCLUSIONS
  Perceived risk should be taken into consideration when studying the effect of HIV knowledge on sexual risk behavior of IDUs. Findings may help us better understand negative effects of fear arousing interventions as a part of HIV prevention media campaigns.
authors.affiliation: Faculty of Medicine, Qom University of Medical Sciences , Qom , Iran.
authors.forename: Gholamhossein
authors.initials: G
authors.lastname: Noroozinejad
authors.affiliation: Department of Psychology, Bu-Ali Sina University , Hamedan , Iran.
authors.forename: Mosaieb
authors.initials: M
authors.lastname: Yarmohmmadi Vasel
authors.affiliation: Universal Network for Health Information Dissemination and Exchange (UNHIDE) , Tehran , Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Bazrafkan
authors.affiliation: Medicine and Health Promotion Institute , Tehran , Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Sehat
authors.affiliation: AIDS Prevention and Control Committee, Welfare Organization State , Tehran , Iran.
authors.forename: Majid
authors.initials: M
authors.lastname: Rezazadeh
authors.affiliation: Behavioral Sciences Research Center, Baqiyatallah Medical Sciences University , Tehran , Iran.
authors.forename: Khodabakhsh
authors.initials: K
authors.lastname: Ahmadi
keywords: HIV knowledge; interaction effect; moderator; perceived risk; sexual risk behavior