Many of the problems that impact adolescent health are preventable because they stem from behavioural choices, and not physical roots. It is for this reason that clinical research with adolescents often incorporates behavioural assessment and intervention strategy into clinical research. If they do not, they are not addressing issues that place adolescents at the greatest risk.

Clinical trials are experiments or quasi-experiments that test hypotheses concerning the effects (favourable or unfavourable) of intervention techniques applied to individuals. They may be tests of therapeutic agents, devices, regimens or procedures (therapeutic trials), of preventive ones (prophylactic trials), or of rehabilitative or educational procedures and so on.

An overview of the clinical trial process shows a six-step process”

• Step 1: Specify intervention, programme theory, and outcomes.
• Step 2: Establish unit of assignment and eligible population
• Step 3: Randomly assign a sample of eligible population to treatment and control groups
• Step 4: Collect baseline data from both groups. Prepare baseline report
• Step 5: Collect data about implementation (and possibly mid-term outcomes). Prepare midline report
• Step 6: Collect endline data from both groups. Calculate impact. Prepare final report and recommendations

Types of clinical trial

• Parallel (concurrent controls)
• External controls
• ‘Self-controlled’
• Randomised controlled

A typical randomised controlled trial

According to UNICEF, a randomised controlled trial (RCT) is an experimental form of impact evaluation in which the population receiving the programme or policy intervention is chosen at random from the eligible population, and a control group is also chosen at random from the same eligible population.

A randomised controlled trial tests the extent to which specific, planned impacts are being achieved. The distinguishing feature of an randomised control trial is the random assignment of units (e.g. people, schools, villages, etc.) to the intervention or control groups. One of its strengths is that it provides a very powerful response to questions of causality, helping evaluators and programme implementers to know that what is being achieved is as a result of the intervention and not anything else.

Random sampling refers to how a sample is drawn from one or more populations. It is random because each member of the sampling frame has the same chance of being included in the sample. The meaning of random in research is very different to the meaning of the word (an adjective) in English.

Random assignment refers to how individuals or groups are assigned to either a treatment group or a control group.

• Eligible? → If not, exclude
• Consent? → If not, exclude
• Randomize to Groups A and B
• Treat (subjects may be blinded to treatment)
• Follow up all members of Groups A and B
• Compare outcomes or changes in Groups A and B

Sound scientific clinical investigation almost always demands that a control group be used against which the new intervention can be compared. Randomization is the preferred way of assigning participants to control and intervention groups.