When must informed consent be obtained from study participants?

Informed consent must be obtained from study participants before any screening process begins to ensure that individuals are fully aware of the study's purpose, procedures, risks, and potential benefits. This early acquisition of consent is crucial because it allows participants to make informed decisions about their involvement from the outset, prior to any assessments that could affect their eligibility or willingness to participate.

Obtaining consent at this stage respects the ethical principle of autonomy, enabling individuals to understand what they are agreeing to before any research activities commence. It is also important for compliance with regulatory requirements that demand consent be fully informed and voluntary.

In contrast, waiting until after initial assessments, during random assignment, or at the beginning of the treatment phase would not align with ethical standards, as participants would not have the opportunity to make decisions based on complete information from the very beginning of the study process.