Table 2.

Studies included in review by design type

Study design	Study
1. Commitment intervention versus minimal contact/ assessment only	Clifford 1991 [36], Balk-Møller 2017 [38], Maruyama 2010 [40], Kegler 2016 [41]
2. Commitment intervention versus same intervention without commitment condition and variation of commitment condition	Nyer 2010 [39]
3. Commitment intervention versus minimal contact/ assessment, same intervention without commitment condition, and variation of commitment condition	Franzini 1980 [42]
4. Commitment intervention versus variation(s) of commitment condition only	Black 1983 [43], Craighead 1989 [45], Dubbert 1984 [46], Ureda 1980 [44]