title: Exercise reinforcement, stress, and β-endorphins: an initial examination of exercise in anabolic-androgenic steroid dependence.
abstract: BACKGROUND
  Anabolic-androgenic steroids (AASs) are abused primarily in the context of intense exercise and for the purposes of increasing muscle mass as opposed to drug-induced euphoria. AASs also modulate the HPA axis and may increase the reinforcing value of exercise through changes to stress hormone and endorphin release. To test this hypothesis, 26 adult males drawn from a larger study on AAS use completed a progressive ratio task designed to examine the reinforcing value of exercise relative to financial reinforcer.
  
  
  METHODS
  Sixteen experienced and current users (8 on-cycle, 8 off-cycle) and 10 controls matched on quantity×frequency of exercise, age, and education abstained from exercise for 24 h prior to testing and provided 24-h cortisol, plasma cortisol, ACTH, β-endorphin samples, and measures of mood, compulsive exercise, and body image.
  
  
  RESULTS
  Between group differences indicated that on-cycle AAS users had the highest β-endorphin levels, lowest cortisol levels, higher ACTH levels than controls. Conversely, off-cycle AAS users had the highest cortisol and ACTH levels, but the lowest β-endorphin levels. Exercise value was positively correlated with β-endorphin and symptoms of AAS dependence.
  
  
  CONCLUSIONS
  The HPA response to AASs may explain why AASs are reinforcing in humans and exercise may play a key role in the development of AAS dependence.
authors.affiliation: Department of Psychiatry, Ichan School of School of Medicine at Mount Sinai, New York, NY, USA. Electronic address: hildebtb@hotmail.com.
authors.forename: Tom
authors.initials: T
authors.lastname: Hildebrandt
authors.affiliation: Department of Psychiatry, Ichan School of School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Sydney
authors.initials: S
authors.lastname: Shope
authors.affiliation: Department of Psychiatry, Ichan School of School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Eleanna
authors.initials: E
authors.lastname: Varangis
authors.affiliation: Department of Psychiatry, New York University, New York, NY, USA.
authors.forename: Diane
authors.initials: D
authors.lastname: Klein
authors.affiliation: Rockefeller University, New York, NY, USA.
authors.forename: Donald W
authors.initials: DW
authors.lastname: Pfaff
authors.affiliation: Department of Psychiatry, Ichan School of School of Medicine at Mount Sinai, New York, NY, USA; James J. Peters Veterans Affairs Medical Center, Bronx, New York, NY, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Yehuda
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000339:Affect / Q000187:drug effects; D045930:Anabolic Agents; D000728:Androgens; D001828:Body Image / Q000523:psychology; D016022:Case-Control Studies; D003192:Compulsive Behavior / Q000503:physiopathology; D015444:Exercise / Q000523:psychology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008875:Middle Aged; D012054:Reinforcement, Psychology; D013315:Stress, Psychological / Q000503:physiopathology*; D019966:Substance-Related Disorders / Q000097:blood / Q000523:psychology*; D055815:Young Adult; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D045930:Anabolic Agents; D000728:Androgens; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone
keywords: ACTH; Anabolic–androgenic steroids; Compulsive exercise; Cortisol; Drug dependence.; β-endorphin