Understanding adolescents: a guide for researchers.
Subject: Adolescence (Research)
Adolescence (Health aspects)
Adolescence (Psychological aspects)
Author: Turner-Henson, Anne
Pub Date: 06/01/2005
Publication: Name: Journal of Neuroscience Nursing Publisher: American Association of Neuroscience Nurses Audience: Professional Format: Magazine/Journal Subject: Health care industry Copyright: COPYRIGHT 2005 American Association of Neuroscience Nurses ISSN: 0888-0395
Issue: Date: June, 2005 Source Volume: 37 Source Issue: 3
Topic: Event Code: 310 Science & research
Accession Number: 135815917
Full Text: Adolescent-focused research has lead to significant improvements in our understanding of adolescent health, as well as the development of innovative healthcare interventions for this vulnerable population. The range of adolescent research has produced new insight into the ways adolescents differ from children and adults (Society for Adolescent Medicine, 2003). Federal regulations governing the conduct of research in adolescent populations, however, often fail to distinguish adolescents from children as research participants.

Adolescents represent a vulnerable population for study because of the rapid changes that occur during this period of life. Key characteristics of adolescents that can influence research include dramatic and relatively rapid biological changes, with a great deal of individual variation; an evolving developmental and cognitive maturity; feelings of lacking authority and control in healthcare settings; and dependence on parents and healthcare providers to make informed decisions about their care (Broome, Richards, & Hall, 2001).

Conducting research with adolescent populations requires maintenance of a balance between scientific responsibility and participant welfare (Fisher, Higgins-D'Alessandro, Rau, Kuther, & Belanger, 1996). Maintaining this balance can be an ethical challenge, especially when conducting research involving adolescents with neurological conditions. Nurses who work with adolescents with neurological problems often face multiple and complex issues related to diverse cognitive and developmental concerns. Concerns regarding consent and protection of human rights arise for this population, as well. This article provides an overview of adolescents' participation in research studies, examining physical, psychosocial, and cognitive developmental perspectives, as well as implications for neuroscience nursing research and practice.

Physical Development

The age range for adolescence generally is defined as 10-21 years of age. Three age subgroupings are recognized: early adolescence (10-14); middle adolescence (15-17); and late adolescence (18-21) (Elliott & Feldman, 1990). Human growth patterns generally are predictable, but each adolescent follows his or her own unique timetable. Based solely on chronological age, adolescents vary widely in their size, metabolic rate, and physical development. For example, one could view a group of early-adolescent males age 14 years and note vast differences in height, weight, physical appearance, and pubertal changes.

Pubertal changes during adolescence are variable in both timing and rate, and often not associated with chronological age. Distinct racial differences have been noted in gender-specific fat distribution and the progression of puberty among African Americans, White Americans, and Asian Americans (He et al., 2004). Asian American adolescents were found to have greater gynoid fat mass (less female in appearance) among females, and less gynoid fat mass (less male in appearance) in males. Hormonal changes drive many somatic changes during early adolescence (Petersen & Leffert, 1995). Physical changes during this period include genital development, breast development (females), pubic and axillary hair development, facial hair and voice deepening (males), skin changes, and rapid changes in both height and weight (Tanner, 1962). While these physical changes are associated with sexual and physical maturation, they do not always reflect maturation in other areas, such as cognitive and psychosocial development (Petersen & Leffert, 1995). Sexual maturation can influence an adolescent's self-image and overall well-being. Increased sexual maturation generally is viewed more positively for males and more negatively for females (Dorn, Crockett, & Petersen, 1988). Prevailing societal views of body size that prize thin physiques often conflict with female body composition changes during puberty (e.g., increases in weight and fat deposits; Petersen & Leffert, 1995).

Of particular significance to adolescent research are pubertal effects on metabolism. Differences in metabolism, drug pharmacokinetics, and therapeutic response between adult and adolescent populations have been relatively unknown (Rogers, 1994). Recent efforts by the Food and Drug Administration (FDA; Best Pharmaceuticals for Children Act of 2002, P.L. 107-109) however, have encouraged pharmaceutical companies to develop safe, effective drug formulations for children and adolescents, and the Pediatric Research Equity Act of 2003 (P.L. 108-155) gives the FDA the authority to require pediatric studies of certain drugs and biological products (Institute of Medicine, 2004).

Much remains unknown about the specific effects of puberty on drug efficacy or pharmacokinetics. Physiological changes during the adolescent period are dependent upon the specific pathways of clearance. Drug clearance and half-life clearance during puberty have been found to move toward adult levels (Goodman, Gilman, Limbird, & Hardman, 2001). For example, drug metabolism and clearance begin to closely resemble that of adults when adolescents reach the fourth Tanner stage. Female physical characteristics include formation of breast areolae secondary mound, pubic hair of adult quality; male physical characteristics include continued growth in length and width of penis, pubic hair of adult quality, axillary hair, voice changes, and acne vulgaris (Tanner, 1962).

Psychosocial and Cognitive Development

As with physical development, psychosocial and cognitive development also can vary widely during adolescence. The gradual and variable development of social and emotional maturity, as well as an increasing sense of self and development of autonomy, characterize adolescence. Researchers must consider adolescents' decision-making and information-processing capacities and their relative stage of self-determination in managing their participation in studies.

The rudimentary capacities for self-determination begin as adolescents begin to separate from their parents. During this period, adolescents begin to develop more and more control over their personal lives, gain greater insights, and exercise greater control over their immediate environment. Adolescence is characterized by an emerging capacity to make independent and intelligent decisions, and this capacity is linked to the adolescent's developing cognition and previous life experiences. Adolescents may mirror the decision-making processes of adults when it comes to their own personal health outcomes, but their own cognitive processes often are underestimated (Broome, et al., 2001).

Experience and emotional development play a key role in decision making for adolescents (Petersen & Leffert, 1995). Novel situations (e.g., a new diagnosis, first-time hospitalization, etc.) may tax an adolescent's cognitive and decision-making skills. When an adolescent lacks experience in certain situations, he or she may respond impulsively without considering the consequences of their actions or alternative choices, or may become more dependent upon an adult for help in the decision-making process. Adolescents under extreme stress may be unlikely to reason effectively, and lack the ability to process information related to the risks and benefits of research participation. Throughout adolescence, decision-making capacity does increase, however, as well as the ability to understand and consider future consequences also increases (Petersen & Leffert, 1995). Though, this capacity for decision making is highly variable during the adolescent period, and may be heavily dependent upon the cognitive and intellectual capacities of the adolescent.

An adolescent with a chronic neurological condition and no cognitive impairment, for example, may exhibit higher levels of self-determination as a result of experience in healthcare settings (e.g., frequent healthcare visits or hospitalizations), and an increased level of sophistication about and comfort within healthcare settings. An adolescent (same chronological age) with a cognitive impairment, however, may exhibit a greater degree of dependence on parents. Other significant life experiences, such as frequent or prolonged hospitalizations, unexpected pregnancy, or experience with the criminal justice system, also may influence emotional development and enhance self-determination capacities.

Dependence on adults, particularly parents, may vary greatly during adolescence. Early adolescent behaviors may range from clinging to rebellious. Children in middle adolescence may develop stabilized and satisfactory relationships with their parents. As they move into late adolescence, they may more strongly identify with peer group members and no longer view their parents as final authorities.

In conducting research, it is important to identify and understand the relationship between adolescents and parents as well as their perceived power differences. Adolescents may perceive themselves as less powerful than their parents or healthcare providers, and therefore be less likely to exercise free will. They may be distrustful of adults, show deference to parental dictates, or be reluctant to express their true feelings or concerns.

It also is important for researchers to understand influences on adolescents' understanding of or participation in research. Broome (1999) has described the developmental differences regarding how children and adolescents may understand their participation in research (Table 1). These differences may be viewed in terms of their understanding, voluntariness, and autonomy. While adolescents generally can understand at a level of comprehension, voluntariness, and autonomy to provide an informed consent, differences may occur based upon an adolescent's particular situation (e.g., chronic condition, prior experiences, cognitive functioning and abilities) or setting (e.g., hospital vs. community).

Researchers also must consider, "therapeutic misconception," which occurs when the boundary between research and standard treatment is blurred for study participants (Nelson & Rushton, 2001). While this phenomenon is relevant for study participants of all ages and developmental levels, it is particularly important for researchers to explain the difference between standard health treatment and research to adolescents. For example, a researcher may need an extra tube of blood for a research study, and drawing blood during every clinical visit may be a part of standard clinical care. The researcher should explain to the adolescent that drawing blood is part of what normally would happen on that clinical visit, but, for the research, one extra tube of blood needs to be obtained. Researchers should review with the patient the possible risks and discomfort (if any) associated with drawing the extra tube of blood.

Assessing the risk of coercion is important at any chronological age, but for adolescent research participants, it is especially important. Overt coercion, which is easy for researchers to spot, usually includes an overbearing parent or healthcare provider who "harasses" an adolescent into participation. Instances of subtle coercion, such as intimidation by authority figures, feelings of wanting to please, intimidation by the environment, contrariness of adolescents, and peer influence, are more difficult to recognize. Researchers are ethically bound to support autonomy in their research participants; therefore, it is critical to consider adolescents' evolving emotional development and prior experiences if they are to be involved in research.

Implications for Research and Practice

Cognitive development and functioning may be impaired in adolescents with neurological conditions because many of these conditions have related neuropathology that affects the brain. Adolescents with neurological conditions may have lifelong impaired cognitive functioning (i.e., delayed developmental functioning exhibited by slowed or impaired cognitive functioning), or, for new-onset conditions, a rapid or gradual reduction in cognitive functioning (e.g., closed-head-injury trauma). Williams (2002) provided general guidelines for consent and data collection in vulnerable populations with neurological conditions, though the focus was primarily on adult populations. Conducting research with adolescents, particularly adolescents with neurological conditions, requires a thorough understanding of the neurological condition the relevant developmental issues, and the processes of involving adolescents in research.

The informed consent must comprise a process, not just the signing of forms. In research involving children and adolescents, however, an additional form of consent, an assent form is used. An assent form provides information in concrete, age-appropriate format and terms that explain the purpose of the research, what the participant will be asked to do, the procedures that will take place, and the risks and benefits of participation (Broome, 1999). The assent form is used for children and adolescents 7-17 years of age, with the upper age limit dependent upon the age of majority of the participant's home state.

Federal regulations regarding the conditions under which parental consent and child and adolescent assent to participate are flexible and meant to serve as a framework for research (Department of Health and Human Services, 1986); individual institutional review board (IRB) opinions vary on the use of assent forms in pediatric research. Professional organizations (the American Academy of Pediatrics [AAP], the Society for Adolescent Medicine [SAM], and the Society of Pediatric Nurses [SPN]) all affirm the need to be inclusive and respect the decision-making abilities of children and adolescents (American Academy of Pediatrics, 1995; Society for Adolescent Medicine, 2003; Society of Pediatric Nurses, 2003). A Web site outlining guidelines for child and adolescent assent in clinical research trials may be found at the National Cancer Institute Web site, and are available online at http://tinyurl.com/4xvem.

The assent or consent process should build upon the adolescent's cognitive and decision-making abilities, as well as his or her understanding of the research. Make no assumptions about their understanding. For an adolescent to provide assent (or consent), he or she must (a) have the legal capacity to consent (dependent upon state law), (b) be allowed to exercise free will without encountering deceit, duress, fraud, or coercion, (c) have sufficient knowledge and comprehension of the elements of the research (heavily dependent upon the adolescent's cognitive abilities (Broome, 1999), and (d) decide whether to participate--a decision that the researcher must respect regardless of the parental decision.

A power imbalance exists when adolescents (particularly younger adolescents) feel the need to please others, especially in situations that are new to them or in which they feel less comfortable. They may view adults, particularly their parents and healthcare providers (or the researcher), as the ultimate authorities. Researchers and nurses must be aware of and accountable for the power they hold in influencing adolescents' decisions to participate in research (Broome, 1999), and they must be aware that the voluntary and informed consent principles may be easily and inadvertently vio lated (Nelson & Rushton, 2001).

Obtaining an adolescent's agreement to participate in a study should be done separately from obtaining consent from parents. Adolescents should be allowed to read (or be read to) the assent or consent form in a room apart from their parents. Age and developmentally appropriate strategies, which may include written materials, verbal explanations, diagrams, peer discussions, videotapes, etc., should be used (Broome, 1999). Adolescents must know their opinions are valuable and will be respected, and the information they provide will be protected and kept confidential. As with the consent process for adults, adolescents should receive a copy of the assent form to take home. At subsequent data collection points and visits, the adolescent should be given an opportunity to ask questions.

Involving adolescents in the consent or assent process raises the possibility of refusals. Refusals and confidentiality must be respected and upheld in adolescent populations (Broome, 1999). Refusal (also referred to as dissent) is defined as objection to the research (Broome, 1999). Federal regulations offer no firm guidelines regarding how to handle refusals by adolescents; instead, the guidelines recommend that individual IRBs make decisions on a case-by-case basis. As with the recommendations for assent, professional organizations (AAP, SAM, SPN) take the position that adolescent refusal to participate in research should be considered binding (even in instances of parental permission), especially in cases of nontherapeutic research.

In adolescents with full capacity (absence of cognitive delay), assent is required and researchers should respect refusal. In adolescents with developing capacity, if the study involves interventions that could be therapeutic but not life-saving, every attempt should be made to persuade rather than override refusals, though refusals still may be binding in certain situations. In cases in which the study involves potentially life-saving interventions or therapeutic studies (e.g., direct benefit is expected, and therapy is available only in the context of the research study), refusals should be overridden. Overriding an adolescent's refusal to participate should be considered carefully, with every attempt made to understand the refusal (e.g., fear related to the procedure).


The research establishment often has a "one size fits all" mentality with regard to the research process (Broome, Richards, & Hall, 2001). Consent processes are standardized, and federal regulations have been established to protect both adults and children. As a research population, however, adolescents often are conceptualized as children.

Adolescents represent a vulnerable study population. To effectively and ethically involve adolescents in research, researchers must understand and integrate knowledge of the variability in physical, cognitive, and psychosocial developmental factors, as well as an understanding of the research processes needed to protect adolescents. Adolescents need to be active participants in the decision-making process (e.g., assent/consent, knowledge of the risks and benefits, etc.). Researchers must be aware of and accountable for the power they hold in influencing adolescents' decisions to participate in research, and they must bear in mind that the voluntary and informed consent principles may be easily and inadvertently violated (Nelson & Rushton, 2001).


This paper was made possible in part by MCHB Leadership and Education in Adolescent Health (LEAH), T71MC00017-02-01.


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Questions or comments about this article may be directed to Anne Turner-Henson, DSN RN, at the University of Alabama-Birmingham School of Nursing, 1530 3rd Ave. South, Birmingham, AL 35294-1210, or by e-mail at turnhena@uab.edu. She is a professor at UAB School of Nursing, UAB School of Medicine (Adolescent Medicine).
Table 1. Developmental Differences Influencing Participation in
Research (Broome, 1999)

Component       School-Age                     Adolescent

Understanding   * More likely to see locus     * Can see value of
 of research      of control as external,        others' perspective
                  which influences ability     * Can weigh alternatives
                  to acquire or seek           * Can entertain
                  information                    alternative treatments
                * Understanding is based         and risks
                  upon previous experience       simultaneously
                                               * Can think in
                                                 hypothetical terms

Voluntariness   * 7- to 9-year-old children    * Has a decreased need
                  are less conforming to         for approval
                  pressure than 10- to         * Compares own actions
                  14-year-old adolescents        with actions of people
                * < 8-year-old children are      similar to self
                  authority-oriented, avoid

Autonomy        * Respects medical authority   * Understands medical
                * Is bound by rules, likes       authority is dependent
                  to comply                      upon patient's
                * Decides about propriety of     agreement to comply
                  decision based upon          * Judges merits of
                  whether it satisfies self      action on ability to
                  or others close to self        help others
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