Text box: Health interventions and complex adaptive systems

Interventions that were shown to be successful on a small scale in a controlled research context may not be effective on a larger scale because of contextual differences, such as levels of health system development, ecological factors, social and cultural differences.
The process of implementing an intervention rarely proceeds according to plan and often has to be rapidly adapted to suit an alternative and/or changing context.
The ability of implementation managers to exercise control over the behaviour of providers, communities and even their own staff is, in practice, often highly constrained by the organizational environment.
Apparently simple technical interventions can exhibit CAS behaviours when multiple stakeholder groups and independent factors interact.
Substantial interventions can sometimes result in very limited outcomes and conversely, relatively small inputs can have major positive/negative consequences.