The Relationship of TLI, Life Stress, and SUD

Introduction: Our previous study results demonstrate that TLI, a measure of liability for substance use disorder, as measured at age 10-12, is associated with an increased risk of current drug use at age 19, which in turn is associated with substance use disorder (SUD) at age 22.  However, it has been unclear whether life stress moderates that relationship, or whether stress predicts SUD.  This study assessed whether life stress moderates or predicts the relationship between TLI and SUD.

Methods: The subjects in this ongoing study were male offspring of men with a lifetime history of a SUD (SUD + probands, N=95, called the HAR group) and men with no lifetime history of a SUD (SUD –  probands, N=96, called the LAR group).  These subjects had been recruited for participation in a longitudinal project designed to elucidate the etiology of SUD, which was conducted at the Center for Education and Drug Abuse Research (CEDAR).  Probands were considered to have a lifetime history of SUDs if they met DSM-III-R dependence or abuse criteria for any substance other than nicotine, caffeine, or alcohol.  The participants were initially recruited when they were 10-12 years of age, and subsequent assessments were conducted at age 12-14, 16, 19, and then annually until age 30.  Stress was measured as the sum of two groups of stress-related subscale scores (“Challenging-Uncontaminated Composite” score and “Negative Outcome Composite” score) on the Life Events Questionnaire (LEQ).  Path analysis (mediation analyses) was used to assess whether life stress assessed at age 20 moderates the relationship between TLI and SUD.  Among the covariates included in the analyses is a measure of heritable liability to substance use disorders developed at CEDAR, known as the Transmissible Liability Index, or TLI, measured at study entry.

Results: The sample included 191 males, including 73% white, 25% black, and 2% other subjects.  By the age 22 assessment, 35% of the subjects had been diagnosed with a SUD.  The mean stress level was 4.33 +/- 4.00 of a possible 54 items (range 0-26), and the mean TLI was 0.13 +/- 0.88. Model fit statistic: chi-square=2.14, df=4, p=0.71, RMSEA<0.0001, CFI=0.99, TLI=0.99.  Stress at age 20 significantly predicted SUD at age 22 (.22, p<.05); however, stress did not moderate the relationship between the TLI assessed at age 10-12 and SUD.

Conclusions: These findings suggest that stress at age 20 predicts SUD at age 22 among teenagers making the transition to young adulthood beyond the effects of TLI and demographic factors, but that stress does not moderate the relationship between TLI and SUD.

Supported by P50 DA05605, R01 DA019142, R01 AA015173, K02 DA017822, K24 AA015320, K05 DA031248