The goal of a clinical study is to determine the factors associated with a disease and to assess the efficacy and safety of an investigational drug, procedure, or device. Since clinical study designs vary due to unique requirements of individual studies, the aims of this report are to educate researchers on the different types of studies and to assist researchers in choosing the optimal study type to fulfill their individual requirements. Clinical studies are classified into the two main types, observational studies and clinical trials, depending on the presence or absence of an intervention. Observational studies include case-control studies, cohort studies, and cross-sectional studies. Case-control and cohort studies may be prospective or retrospective, and case-control studies may be nested or not. Clinical trials may be pragmatic and may be controlled or noncontrolled; randomized or nonrandomized; open label or blinded; and parallel, crossover, or factorial. These observational and clinical trial designs are reviewed. Each type of clinical study has advantages and disadvantages. Therefore, researchers must consider these in choosing the design best suited for achieving their study objectives.
Citations
Citations to this article as recorded by
Demystifying Clinical Research Trials Sami V. Abate, Catherine E. Vasquez Nurse Leader.2026; 24(1): 102635. CrossRef
Innovative oncology trial designs: Time to act – A review with recommendations of the Cancer Drug Development Forum Rosa Giuliani, Nafsika Kronidou-Horst, Christina Yap, Aáron Sosa Mejia, Lada Leyens, Theodor Framke, Fergus Sweeney, Laurence Collette, Rachel Giles, Jan Bogaerts, Peter van de Ven, Stefan N. Symeonides Journal of Cancer Policy.2026; 47: 100696. CrossRef
Effect of norepinephrine initiation timing on mortality in septic shock: a multicenter cohort study Jung Won Choi, Tae Gun Shin, Seung Jin Maeng, Sung Yeon Hwang, Sang-Min Kim, Won Young Kim, Kyuseok Kim, Sung-Joon Park, Sung-Hyuk Choi, Sejoong Ahn, Woon Yong Kwon, Taeyoung Kong, Sung Phil Chung, Byuk Sung Ko, Tae Ho Lim BMC Anesthesiology.2026;[Epub] CrossRef
Longevity of different in-office treatments for dentin hypersensitivity: A 6-month randomized and parallel clinical trial Fernanda de Souza e Silva Ramos, André Luiz Fraga Briso, Érika Mayumi Omoto, Edgar Dutra Zanotto, Paulo Henrique dos Santos, Bruna Perazza, Ticiane Cestari Fagundes, Esra Cengiz Yanardag PLOS One.2026; 21(2): e0342651. CrossRef
Selective Otolithic and Semicircular Canal Dysfunction: Insights from VEMP and vHIT Pavol Skacik, Stefan Sivak, Egon Kurca Journal of Clinical Medicine.2026; 15(10): 3944. CrossRef
Reply to: assessing the association between postpartum depression and caesarean section under general anaesthesia Yu-Ting Hung, Si-Cheng Xie European Journal of Anaesthesiology.2026; 43(7): 642. CrossRef
Neoadjuvant PD-1-Based Immunotherapy in Localized dMMR/MSI-H Colorectal Cancer: A Systematic Review and Arm-Based Meta-Analysis Mohammed M. Alruwaili, Yehia Nabil, Yousef Alanazi, Helal G. Alanazi, Abdulrahman A. Alahmari, Emad Alqassim, Baraah Abu Alsel, Manal S. Fawzy Cancers.2026; 18(15): 2436. CrossRef
Comment on “Comparison of oral gabapentin with nebulized dexmedetomidine for anxiolysis and hemodynamic stability in awake fiberoptic intubation: A randomized controlled study” Nitin Choudhary, Rohan Magoon Medical Journal Armed Forces India.2026;[Epub] CrossRef
Long-term glycemic variability and risk of peripheral artery disease: a systematic review and meta-analysis of cohort studies Jie Xia, Qionghui Peng, Lei Chen, Chiqiong Liu, Ting Zhu PeerJ.2026; 14: e21686. CrossRef
Clinical Trials in Adult Communication and Swallowing Disorders: Building the Evidence Base for Patient-Centered Care Leora R. Cherney Journal of Speech, Language, and Hearing Research.2026; : 1. CrossRef
Artificial intelligence-enabled obesity prediction: A systematic review of cohort data analysis Sharareh Rostam Niakan Kalhori, Farid Najafi, Hajar Hasannejadasl, Soroush Heydari International Journal of Medical Informatics.2025; 196: 105804. CrossRef
A Mobile-Based Approach to Enhance Knowledge of Infant and Young Child Feeding Among Teenage Mothers in Nigeria: A Randomized Controlled Trial Mercy E. Sosanya, Oluwatosin D. Adesanya, Hauwa E. Rufai, Jeanne H. Freeland-Graves Nutrients.2025; 17(3): 414. CrossRef
In-Utero Maternal-to-Fetal Transmission of COVID-19: An Immunological and Virological Study in the Eastern Province of Saudi Arabia Hibah Alzayer, Basavaraja Hunasemarada, Arwa Alumran, Shaikha Aldossary, Reem Al Dossary Infection and Drug Resistance.2025; Volume 18: 1393. CrossRef
Navigating the Multiverse: a Hitchhiker’s guide to selecting harmonization methods for multimodal biomedical data Murali Aadhitya Magateshvaren Saras, Mithun K Mitra, Sonika Tyagi Biology Methods and Protocols.2025;[Epub] CrossRef
Brazilian green propolis effect on biochemical parameters and dietary intake in people living with diabetes Gabriela Fonseca Lopes, Paula Brumana Corrêa, Fernando Luiz Pereira de Oliveira, Nathalia Sernizon Guimarães, Nícia Pedreira Soares, Andrea Yukie Arikawa, Aline da Silva Miranda de Menezes e Souza, Rachel Basques Caligiorne, Luciana Araújo Marques, Nancy Diabetes Research and Clinical Practice.2025; 225: 112236. CrossRef
Outcomes of a Risk-Stratified Protocol for Preventing Peristomal Skin Complications in Patients with an Ostomy: A Cohort Study Francesco Carlo Denti, Eliana Guerra, Francesca Caroppo, Pietro Abruzzese, Fabrizio Alessi, Filippo Barone, Pasqualina Bernardino, Massimiliano Bergamini, Maria Cristina Bernardo, Gloria Bosio, Paula Carp, Manuela Cecconello, Annalinda Cerchier, Francesca Nursing Reports.2025; 15(5): 179. CrossRef
A critical review on the impacts of β-glucans on gut microbiota and human health Great Iruoghene Edo, Alice Njolke Mafe, Ali B.M. Ali, Patrick Othuke Akpoghelie, Emad Yousif, Endurance Fegor Isoje, Ufuoma Augustina Igbuku, Khalid Zainulabdeen, Joseph Oghenewogaga Owheruo, Arthur Efeoghene Athan Essaghah, Huzaifa Umar, Dina S. Ahmed, A The Microbe.2025; 7: 100394. CrossRef
Comprehensive analysis of Mendelian randomization and scRNA-seq identify key prognostic genes and relevant functional roles in colorectal cancer Meng Hu, Haotian Dong, Chujia Chen, Chengyuan Ye, Jianing Yan, Xuan Yu, Guoliang Ye, Yongfu Shao Scientific Reports.2025;[Epub] CrossRef
Expanding horizons in esophageal squamous cell carcinoma: The promise of induction chemoimmunotherapy with radiotherapy Wenxue Ma, Natalia Baran World Journal of Clinical Oncology.2025;[Epub] CrossRef
Unveiling the science of drug development: strategies, successes, and challenges M. Shakir Hussain, Ajit Kumar Mishra, Rishabh Pandey International Journal of Basic & Clinical Pharmacology.2025; 14(5): 882. CrossRef
Concerns regarding the article “Comparative clinical observations following introduction of a new polyvalent antivenom for snakebite envenoming in northern Nigeria” by Hamman et al. Toxicon 266 (2025) 108510 Vishwas B. Sovani Toxicon.2025; 268: 108593. CrossRef
Association between atherogenic index of plasma and incident aortic disease: a population-based prospective analysis Cuihong Tian, Xiao Wang, Liang Tao, Wanyi Wei, Xuan Zhang, Haoxian Tang, Yequn Chen, Xuerui Tan Open Heart.2025; 12(2): e003511. CrossRef
Botulinum toxin A in idiopathic overactive bladder: a narrative review of 5410 cases Salim Lachkar, Ahmed Ibrahimi, Imad Boualaoui, Hachem El Sayegh, Yassine Nouini Canadian Journal of Urology.2025; 32(3): 145. CrossRef
Prognostic nutritional indices and functional outcome in patients with subarachnoid hemorrhage: a meta-analysis Sha Luo, Qiuyan Xiang, Muhammad Masroor Hussain, Yiwen Liu Neurosurgical Review.2025;[Epub] CrossRef
The Association Between Nut Consumption and Risk of Depressive Symptoms: A Meta-Analysis of Observational Studies Sohyun Kim, Hyogyeong Lee, Qiao-Yi Chen, Yooheon Park, NaNa Keum Nutrients.2025; 17(24): 3810. CrossRef
Consensus on Core Competencies for Undergraduate Life Sciences Students in Entry-Level Participation in Clinical Trials: A RAND-Modified Delphi Study (Preprint) Ángela Cano, Patricia Cosano-Pérez, Juan José Castón, Diana Corona-Mata, Rosa Ballesteros-Olmedo, Eva Venegas-Moreno, Jaime Perea-Cortés, Concepcion Aranda-Valera, Isabel Machuca, Julian Torre-Cisneros JMIR Human Factors.2025;[Epub] CrossRef
Evaluation of the efficacy of complex analgesic therapy, including a combination of B vitamins, in patients with combination of osteoarthritis and chronic non-specific low back pain (results of an open-label pilot clinical trial) E. S. Filatova, A. E. Karateev, E. L. Shakhramanova, D. A. Ghukasyan, S. Yu. Shkireeva, A. M. Lila Modern Rheumatology Journal.2024; 18(2): 56. CrossRef
Exploring the Prognostic Role of D-dimer Levels in Pancreatic Cancer: A Comprehensive Review of Clinicopathological Associations Sparsh Dixit, Chandrashekhar Mahakalkar, Shivani Kshirsagar, Akansha Hatewar Cureus.2024;[Epub] CrossRef
First
Prev
