Consent in Clinical Trials


What Makes an Effective Informed Consent Form?

Challenges Identified in the Consent Process

  • Complex Information
  • Lack of Understanding and Comprehension
  • Patient Competence

Implementable Approaches to Improve the Consent Process

  • Simplifying Consent Forms
  • Assessing Patient Comprehension
  • Providing Brochures and Information Sheets
  • Audio-Visual Presentations



The Nuremberg Code (1947) and the Declaration of Helsinki (1978) are credited as the origins of informed consent in clinical research. Participants' informed consent is both a legal and ethical requirement in clinical trials.

In a clinical research setting, informed consent is a process whereby participants receive and comprehend all the necessary information of the clinical trial to make a meaningful and autonomous decision. The goal of informed consent in clinical trials is to respect the patient's autonomy and protect participants from harm.

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What Makes an Effective Informed Consent Form?

To make an informed decision, all clinical trial participants should receive and comprehend the provided information appropriately. Four key criteria must be effectively achieved to constitute a meaningful informed consent process. These aspects include comprehension, competence, voluntariness, and information disclosure.

Comprehension implies that participants apprehend all information provided to them. Competence correlates to the patient's ability to make an informed decision regarding participation. Voluntariness means patients decide to participate in clinical trials without coercion or persuasion. Finally, information disclosure involves participants receiving all relevant information about the research, including purpose, benefits, risks, available alternatives, etc.

Challenges Identified in the Consent Process

Several challenges are currently limiting the effectiveness of consent in clinical trials. These include complex information, lack of understanding and comprehension, and patient competence.

The majority of these issues stem from a lack of communication between the research team and participants, leading to insufficient understanding of the clinical trial and ultimately affecting the validity of the informed consent process.

Complex Information

Many consent forms contain complex information, including scientific terminologies and technical jargon due to advancements in medical research. Many informed consent documents are also written at higher levels of readability.

Is Education Key to Accelerating Clinical Trial Participation?

The researcher's legal outlook on consent forms is another factor that makes them complex for participants. Some researchers only view these forms as legal documents required for patient participation, often making them highly complex and challenging to read. Complex consent forms negatively affect the quality of information exchange between the researchers and participants.

Lack of Understanding and Comprehension

Another challenge involves poor understanding and comprehension of consent forms by the trial participants. This includes information regarding the benefits, risks, and significance of participating in clinical studies.

A meta-analysis was conducted to estimate the proportion of clinical trial participants who understand informed consent forms. This review concluded that approximately 75% of participants understood various components of informed consent. Most participants understood the fundamental components, such as the nature and benefits of the study, the freedom to withdraw at any moment, and the voluntary nature of participation.

In contrast, other components of the form were not understood well by many participants, including randomization and placebo, which have not improved over three decades. As a result, researchers and investigators should dedicate more time to making these forms more understandable. Thus, ensuring participants can make an informed and meaningful decision having understood all vital information.

Patient Competence

Patient competence in understanding trial information is also a major challenge that impacts adequate informed consent. This could be due to numerous factors such as age, cognitive disability, mental disorders, and disease progression. Comprehension ability can also be affected by patient anxiety caused by their disease or concerns regarding starting a new treatment during the clinical trial.

Clinical Trials Today: Safety and Informed Consent

Implementable Approaches to Improve the Consent Process

New strategies are now being suggested to improve the consent process in response to these challenges. These include simplifying consent forms, assessing patient comprehension, and audio-visual presentations.

These strategies promote effective communication, enabling participants to receive clear information relevant to their individual learning requirements and encouraging informed decision-making.

Simplifying Consent Forms

The use of simple and direct language and reduced length is recommended to ensure consent forms are easy to understand. In addition, participants' topics that are typically not understood well, including randomization and placebo, should be written and explained in simple terminology. This approach will help to assist individuals with their decision-making.

Assessing Patient Comprehension

To address current issues related to lack of understanding, comprehension test tools can be implemented to assess patients' understanding before signing consent forms. An example of this technique is questionnaires to test participants' understanding.

Providing Brochures and Information Sheets

Another tactic that can be applied is brochures and information sheets. These can be designed to provide complementary information regarding the clinical trial. Comparative studies reveal it improved understanding and patient satisfaction with the use of illustrations and narrative text instead of bullet points and no pictorial depictions in brochures.

Audio-Visual Presentations

Audio-visual presentations are another format in which clinical trial and informed consent information can be provided to participants. These visual presentations can further supplement the written information to consolidate participants' understanding and comprehension further. It also accounts for different learning styles, as some patients may prefer these types of visuals compared to written information documents.

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Informed consent is fundamental to the ethical conduct of clinical trials and is a critical component of the research process. Although consent has become an established procedure for many years, several challenges have been identified affecting validity and effectiveness, mainly lacking communication and participant understanding.

Various innovative communication techniques are now being recommended to improve communication and enhance the consent process to tackle these issues.


  • Kadam, R. (2017). Informed consent process: A step further towards making it meaningful! Perspect Clin Res, 8: 107-112.
  • Tam, N., et al. (2015). Participants' understanding of informed consent in clinical trials over three decades: systematic review and meta-analysis. Bull World Health Organ, 93: 186-198H.

Further Reading

  • All Clinical Trial Content
  • What is a Phase 0 Clinical Trial?
  • What is a Phase 1 Clinical Trial?
  • What is a Phase 2 Clinical Trial?
  • What is a Phase 3 Clinical Trial?

Last Updated: May 18, 2022

Written by

Naveen Dha

Naveen graduated from King’s College London where she attained a Bachelor of Science in Biochemistry. Within this course, she chose to study topics pertaining to the biology of cancer, molecular immunology, molecular biology, and protein structure. Throughout her degree, she partook in writing various practical proposals, reports, and literature reviews whilst also gaining multifaceted laboratory and research experience. It was through these projects that Naveen discovered her interest for scientific writing as it allowed her to remain intellectually curious, creative, and detail-orientated.

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