treatment groups. Other studies experimenting with prizes, vouchers, and in-kind gifts of free nicotine patches showed mixed results, but even positive results disappeared after 6 months.

The use of financial incentives to treat obesity has also gained in popularity, but the evidence regarding efficacy is decidedly more mixed.<sup>4</sup> A recent systematic review of randomized controlled trials of treatments for obesity (Paul-Ebhohimhen and Avenell, 2007) showed no significant effect of the use of financial incentives on weight loss or maintenance at 12 months and 18 months. However, further sub-analysis indicated that large transfers (greater than 1.2% of personal disposable income) had greater impact, as did rewards for behavioral change rather than weight loss, per se, and rewards based on group performance rather than individual results.

The CM literature, overall, offers useful insights into aspects of the conditionality that appear to elicit the desired behavior change. This is an important area of inquiry that has not been sufficiently explored within CCT programs. However, unlike CCT programs, studies of CM have remained largely experimental and have not been brought to scale (Petry 2000; Kane and others 2004). Furthermore, the small sample sizes of study groups – most typically involving groups of 20 to 100, and rarely more than 500 – have made it difficult to detect effects that are statistically significant, much less estimate effect sizes accurately. Also, factorial designs with several treatment arms are common which – in combination with already small sample sizes – leads to even more constraints on power (Kane and others 2004).

# **CCTs and Sexual and Reproductive Health**

While there is growing interest in exploring potential applications of CCTs to sexual and reproductive health, there is understandably concern expressed in some quarters about the ethics of doing so. Individual choices with respect to sexual and reproductive behaviors, more so than perhaps any other area of health, are considered an intensely private affair, and there has traditionally been a great deal of resistance to public interference in women’s and their partners’ right to choose when, whether, and under what circumstances to bear children (Mauldon, 2003).

Nonetheless, CCTs have been used to support sexual and reproductive health policy goals in some countries, and have typically focused either on increasing rates of contraceptive use in communities where birth rates are high (Bangladesh, India) or discouraging teen pregnancies, especially among poor and disadvantaged girls (United States) (Mauldon 2003). More recently, CCTs were used to encourage the uptake of Voluntary Counseling and Testing (VCT) services testing for HIV in a small, randomized control study in Malawi (Thornton, 2006). Interestingly, only the latter example – encouraging the uptake of VCT services – resembles the traditional CCT programs in that the focus is on a simple, and in this case, “one-off” change in behavior. Otherwise the collective experience of applying CCTs to sexual and reproduction health more closely parallels the contingency management approach to behavior change.

> 4 See, for example, Follick (1984); Jeffrey (1978); and Jeffrey (1984).

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