The association of persistent pain with out-patient addiction treatment outcomes and service utilization

To estimate the prevalence of persistent pain among veterans in out-patient addiction treatment and examine associated addiction treatment outcomes and medical and psychiatric service use.

Analysis of data from a prospective randomized controlled trial comparing on-site versus referral primary care of veterans with substance dependence (n = 582), excluding opioid dependence who had at least one follow-up interview during the 12-month study period in a Veterans Affairs (VA) out-patient addiction treatment center.

Pain status was classified as persistent (pain was rated moderate to very severe at all time-points), low (pain was rated none to mild at all time-points) or intermittent (all others). Main outcome measures were addiction treatment retention, addiction severity index (ASI) alcohol and drug composite scores, VA service utilization and treatment costs.

A total of 33.2% of veterans reported persistent pain and 47.3% reported intermittent pain. All groups benefited from addiction treatment, but veterans with persistent pain were in treatment for an estimated 35.1 fewer days [95% confidence interval (CI) = -64.1, -6.1, P = 0.018], less likely to be abstinent from alcohol or drugs at 12 months [odds ratio (OR)(adj) = 0.52; 95% CI = 0.30,0.89; P = 0.018], had worse ASI alcohol composite scores at 12 months (beta(adj) = 0.09; 95% CI = 0.02,0.15; P = 0.007), were more likely to be medically hospitalized (OR(adj) = 2.70; 95% CI = 1.02,7.13; P = 0.046) and had higher total service costs compared to those with low pain ($17 766 versus $13 261, P = 0.012).

Persistent pain is common among veterans in out-patient addiction treatment and is associated with poorer rates of abstinence, worse alcohol use severity and greater service utilization and costs than those with low pain.