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Objective: Evolving privacy and confidentiality regulations make achieving high completion rates in longitudinal studies challenging. Periodically reviewing the methods researchers use to retain participants throughout the follow-up period is important. We review the effectiveness of methods to maximize completion rates in a 1-year longitudinal study of repeat driving-under-the-influence (DUD offenders. Method: During the course of 21 months, we attempted to follow-up with 704 participants of a licensed residential treatment facility for repeat DUI offenders. High rates of lifetime Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, substance-use disorders (97.6%) and nonsubstance- or nongambling-related psychiatric disorders (44.5%) among the sample made tracking participants difficult. To locate participants and complete follow-up interviews, we obtained baseline information, contacted collaterals, sent mailed reminders, searched Internet databases, and gave a monetary incentive for completing study interviews. Results: We located 608 participants with active telephone numbers (87.4%) and completed interviews with 488 (70.1% of the entire eligible sample and 80.3% of those with active telephone numbers), after an average (SD) of 8.6 (9.1) calls (median = 5.0). Increasing the number of calls continued to yield additional completions at 10, 20, and 30 calls; at approximately 40 telephone calls, the potential return for additional calls did not justify the added effort. Conclusions: These results suggest that researchers need to (1) employ more than 10 telephone calls to adequately track difficult-to-follow substance-using populations, and (2) prepare for a subsample of participants who might require more extensive contact. These results highlight the importance of using empirical guidelines to plan estimates for the number of contacts needed to achieve an adequate follow-up completion rate., LONGITUDINAL STUDIES ARE NECESSARY to investigate the antecedents, mediators, and consequences of various complex behavior patterns (e.g., substance-use disorders). However, attrition often limits the value of longitudinal research, particularly research [...]

Abstract Background In an attempt to reduce harm related to gambling problems, an Internet sports betting service provider, bwin Interactive Entertainment, AG (bwin), imposes limits on the amount of money that users can deposit into their online gambling accounts. We examined the effects of these limits on gambling behavior. Methods We compared (1) gambling behavior of those who exceeded deposit limits with those who did not, and (2) gambling behavior before and after exceeding deposit limits. We analyzed 2 years of the actual sports gambling behavior records of 47000 subscribers to bwin. Results Only 160 (0.3%) exceeded deposit limits at least once. Gamblers who exceeded deposit limits evidenced higher average number of bets per active betting day and higher average size of bets than gamblers who did not exceed deposit limits. Comparing the gambling behavior before and after exceeding deposit limits revealed slightly more unfavorable gambling behavior after exceeding deposit limits. Conclusion Our findings indicate that Internet gamblers who exceed deposit limits constitute a group of bettors willing to take high risks; yet, surprisingly, they appear to do this rather successfully because their percentage of losses is lower than others in the sample. However, some of these gamblers exhibit some poor outcomes. Deposit limits might be necessary harm reduction measures to prevent the loss of extremely large amounts of money and cases of bankruptcy. We discuss how these limits might be modified based on our findings.