The Biology of Adolescence

SALLY STANLEYResearch Associate, 4-H Center for Youth Development

Introduction

Sadly, yet not surprisingly, some adultsview the exuberant period of adolescence asa dubious stage of development. Seeingadolescence as a stage of development to bedreaded, rather than anticipated by adults,seems to be encouraged by the popularliterature of today (e.g. Bell, 1987; Caissy,1994). For both teens and adults theliterature ÒwarnsÓ of what is to come. Inspite of very little empirical support, thepopular literature tells teens Òyou may feelfull of energy or lie around and sleep a lot.Your moods may shift quickly,uncontrollably, surprising youÓ (see Bell,1987, p. 5, cf. Buchanan, Eccles, & Becker,1992). Another book, written for parents byCaissy (1994), suggests adolescents aremoody and unpredictable and that negative

interactions between parents and theiradolescents are inevitable. Caissy goes onto suggest that adults should just learn toaccept the Òself-centeredÓ, Òknow-it-allÓ,ÒangryÓ, ÒcriticalÓ and ÒimpulsiveÓbehaviors of teens as ÒnormalÓ behavior forthis age group (Caissy, 1994, p. 53). Thisnegative view of adolescence seems to be allpervasive and may even affect the thinkingof some professionals interacting withtodayÕs youth.

What is the source of this idea thatadolescence is a stage of development to bedreaded? Sigmund Freud (Freud,1905/1962) contended that humans weredriven by their biology. Following in herfatherÕs footsteps, Anna Freud (1969)suggested that adolescents need time toadjust to their new physiological drives. She

then proposed that an inability tounderstand these drives and feelings ledadolescents to convert their drives andfeelings to other feelings such as aggressionor depression. Thus, biology becomes thesource of conflict between adults andadolescents. Yet, conceptualizing thepsychology of adolescence along withphysiology does not necessarily mean wehave to view adolescents as ÒdrivenÓ bythese physiological changes. In fact, thecur ren t zeitgeist encourages anunderstanding of a more complex interactionof both physiological and psychologicalprocesses work ing in concer t(Bronfenbrenner, 1979; Lerner, Lerner, &Tubman, 1989; Scarr & McCartney, 1983).This fresh and more

advanced approach suggests that hormonesprobably do play a role in psychologicaldevelopment, but not quite in the wayenvisioned by Sigmund and Anna Freud, norin the way often portrayed in the popularliterature.

Some empirical studies do show a slight riseof parent-adolescent conflict during puberty.The relationship between puberty andconflict is curvilinear with conflicttemporarily increasing and closenesstemporarily decreasing at the peak ofpubertal maturation; however, this statisticaleffect is very small and has not beenspecifically linked to the hormonal changesof puberty (Blos, 1979; Buchanan, Eccles, &Becker, 1992; Molina & Chassin, 1996;Montemayor, 1986; Paikoff & Brooks-Gunn, 1991; Steinberg, 1989, 1990). Thisslight increase in conflict could just as easilybe explained by shifts and changes withinthe family structure as children turn intoadults (Smetana, 1988). The evidence iscertainly clear that there are tremendousphysical changes during adolescence whichcould possibly make this a challengingperiod of development (Petersen, Susman, &Beard, 1989), but are these changespsychologically and physiologicallyoverwhelming for the adolescent? Shouldparents or adults be concerned or believethat adolescent behaviors, especiallydisparaging ones, stem from hormones? Doparents, or youth professionals need toadjust their comments or guidance toaccommodate for adolescents supposedlyoverwhelmed by hormones? Absolutelynot! None of the evidence available at thistime suggests that the hormonal physiologyof adolescence should lead to negativeexperiences. Thus, it might be more usefuland encouraging for all adults, parents andyouth professionals, to view themetamorphosis from child to adult as anexciting and fun time for all concerned. No

one should ever be led to expect this stage ofdevelopment to be negative and conflictual,but should be encouraged to enjoy theblossoming of children into adults.

With this in mind, the goal of this paper is toencourage parents, youth professionals andother adults to cherish rather than justÒsurviveÓ the period of adolescentdevelopment. Although there is still muchto be learned about the biologicalunderpinnings of this stage of development,this paper will first review the followingareas of current research on adolescentdevelopment:

¥ The hormonal changes ofpuberty and adolescentsÕ moods

¥ The t remendousphysical growth andc h a n g e d u r i n gadolescence

¥ The timing of puberty¥ T h e c u r r e n t

adolescent experienceon average

¥ Parent-adolescentconflict

Then, in conclusion, there will be offered afew suggestions on how to enjoy thebiological changes of adolescence.

The hormonal changes of puberty andadolescentsÕ moods

Adolescence is usually defined as the periodof development from the onset of puberty toadulthood, with the onset of puberty markedby hormonal changes. The general outcomeof puberty is an adult body capable ofreproduction. Hormonal concentrations inblood are low before 8 or 9 years of age(Buchanan, Eccles, & Becker, 1992).Somewhere between 5 and 9 years, thehypothalamic-pituitary-adrenal (HPA) axisis activated, leading to an increase innumerous adrenal steroid hormones. Thesteroid hormones stem from a cholesterolbase and are similar in boys and girls,though varying in quantity. For example,males have more testosterone and femalesless. Females have more estrogen, malesless. Estrogen and testosterone are able tosuppress other gonadotropic hormones suchas LH (Luteinizing Hormone) and FSH(Follicle Stimulating Hormone) untilpuberty. Puberty is caused, in essence, bythe inability of these hormones to continueto suppress the other gonadotropichormones. Exactly why they are unable tocontinue suppressing these hormones is still

unknown (Buchanan, Eccles, & Becker,1992; Cameron, 1990).

In girls, a significant increase in thehormone estradiol is seen at about age 9 or10 years. The increase continues through 13to 14 years. In boys, testosterone levels riseduring sleep somewhere around 10 years ofage, and about six months later, daytimeconcentrations of testosterone increase(Apter, Reinila, & Vihko, 1989). Thenormal range for the onset of puberty isusually around 9.5 years to 13.5 years forboys and 8 years to 13 years in girls(Nottelmann, et al; 1990). Aside fromchanges in concentration of hormones, thereare also cyclic changes, for example themenstrual cycle in girls. Although foradolescents the entire system is transformingand stabilizing into an adult pattern(Buchanan, Eccles, & Becker, 1992), cyclicchanges are true for adults as well (Henry,1992). This period of stabilization ofhormones is most likely the basis of thepopular notion that adolescents, as well astheir behavior and moods, are, in general,unstable and unpredictable.There is still much we do not know aboutpubertal development, so the possibilityexists that the onset and fluctuations ofhormones during puberty can influence themoods of adolescence. For example,receptors for adrenal steroid hormones arefound in the hypothalamus, amygdala andhippocampus, all areas of the brainassociated with affective behaviors andmoods (Buchanan, Eccles, & Becker, 1992;Henry, 1992; Nottelmann et al., 1990).However, even if hormones do affect theseareas of the brain, there is still very littleevidence that hormones affect moods or actdifferentially on adolescents as compared toadults. There is only one study (Larson,Csikszentmihalyi, & Graef, 1980) that mightpossibly support the view that hormonesinfluence moods in adolescents. In this

study, adolescents were to record theirmoods intermittently during the day, whenbuzzed with pagers. Analysis of theserecords did indicate adolescents had moodswings during their day, but this data wasnot correlated with hormonal evidence. Norhas this type of research been done withadults. If we paged adults at various levelsduring their day, we might find that adults,on average, also have mood swings duringthe day. One other study, Diener, Sandvikand Larsen (1985, cf. Buchanan, Eccles, &Becker, 1992) did find a decline in intensityof mood from late adolescence to adulthood,but again we can only assume that intensityincreases during puberty and is driven byhormones. In essence, there is very littleempirical support for the popular belief thatadolescents are Òvictims of raginghormonesÓ (Brooks-Gunn, Warren, &Rosso, 1988, cf. Buchanan, Eccles, &Becker, 1992; Buchanan, 1991; Buchanan,Eccles, & Becker, 1992; Crockett &Petersen, 1987; Larson & Lampman-Petraitis, 1989).

In fact, very few researchers believehormones are the ultimate director ofadolescent behavior (Lerner & Foch, 1987).Greene and Larson (1991) suggest thenotion continues to persist because ofadultsÕ perceptions of teens, as well asresearchersÕ limited knowledge about theinteraction of biology in the adolescent stageof development. Buchanan and colleagues(1992) looked at energy level, restlessnessand concentration, irritability andimpulsiveness, and finding a range ofindividual differences, proposed that someindividuals may be more susceptible to risesin concentration of hormones than others.The individual differences of some mightthen cause the assumption that alladolescents have similar problems. In otherwords, although hormones show no effectson the above behaviors on average, there

may be some adolescents who are moresusceptible to hormones than the averageadolescent.

Other researchers suggest hormonal effectsstem from adolescentsÕ reactions to physicalchange, such as earlier breast developmentthan their peers, rather than hormones per se(Rubin, 1990). Being earlier or later thanthe norm in the timing of puberty, inrelation to the peer group, has beenassociated with negative effects (Brooks-Gunn & Graber, 1994; Petersen, Richmond,& Leffert , 1993; Udry, 1990).Furthermore, the pattern of negative effectsis different for each sex. Reaching pubertyearly appears to have negative effects ongirls whereas late maturity affects boys morenegatively. For example, studies show earlymaturing girls are particularly sensitive toevidencing physical signs of maturation(e.g., breast development) prior to theirpeers, and this sensitivity in turn can lead tolow self-esteem and a poor body image inthese girls. In contrast, late maturing boysfind themselves the last to lose their child-like appearance in their peer group. Beingsmall and looking child-like alongside themore developed boys, at an age when girlsand boys are becoming more interested ineach other, often leads to low self-esteemand poor body image in late maturing boys(Graber & Brooks-Gunn, 1996). Theseeffects are still being researched but suggestthat the hormonal effects of puberty affectself-esteem and personality through socialinteractions and thus play a far moreimportant role in the lives of adolescentsthan portrayed in the popular literature(Buchanan, Eccles, & Becker, 1992). Thepopular literature ignores these ramificationsand instead focuses on the effects ofhormones on adolescent moods.

Buchanan and colleagues (1992) suggest wefocus on the real question, i.e., can we say

that moods and behaviors are differentduring adolescence as compared to otherdevelopmental times? As noted above,hormonal changes are gradually andcyclically changing during the pubertalprocess, yet even adults experience cyclicchanges in hormonal concentrations. Asvery little research has examined therelationship directly (Buchanan, Eccles, &Becker, 1992; Graber & Brooks-Gunn,1996; Petersen, Richmond, & Leffert, 1993),there are no definitive answers. This begsthe question of why the popular literatureand parents continue to accept the idea thatadolescent moods and behaviors are a resultof hormones. If we really want to know ifmoods and behaviors change at puberty,longitudinal studies following adolescentsprior to puberty and through the pubertalprocess will need to be done (Buchanan,Eccles, & Becker, 1992). We are only nowwitnessing an explosion of new studies inadolescent development that are activelymeasuring hormone production in relation tobehavioral patterns (Petersen, Richmond, &Leffert, 1993). Although we know littleabout hormonal changes, many studies havefocused on the morphological changes thattake place during the pubertal process.These changes are summarized below.

The tremendous physical growth andchange during adolescence

Parents of adolescents typically comment onthe vast amount of food this age groupconsumes and may even joke that theiradolescents are Òeating machines.Ó In truth,hormonal changes do lead to an increase innutrient requirements because of the virtualdoubling of body mass and rapid growth thattakes place (Tanner, 1975; 1990).Adolescence is inevitably a time oftremendous physical growth and change aswell as psychological change. The growthspurt, as it is often called, does not proceed

evenly. For both boys and girls, legs usuallygrow first, followed by the trunk. The oldsaying Ònever buy an adolescent boy a suitÓattests to this uneven growth.

The average amount of height gained duringa growth spurt is usually the same for alladolescents. Adult height depends on whenthe growth spurt actually started (Graber &Brooks-Gunn, 1996). Girls begin theirgrowth spurt about two years earlier thanboys, grow about six to seven inches and areusually taller than boys during this timeperiod. Boys grow about 9 inches duringthe growth spurt and by age 14 most boysare taller than girls. Adult men in the UnitedStates on average, are about 4 inches tallerthan women (Tanner, 1990).

Although brain development is completebefore adolescence, the head does growduring this developmental period (Tanner,1975; 1990). In fact, the face actuallychanges from child-like to adult-like as theskull solidifies. Body composition alsochanges. Girls begin to store fat on hips,breasts and upper arms, while boys tend tolose fat and develop muscle. Along withstructural changes, there are changes insensual experiences, for example the sensesof smell and taste increase in intensity.There are sex differences in these changesand the intensity of sensual experiences ismost likely related to reproductive needs ofthe sexes (Tanner, 1990). Changes inmetabolic rate also occur and might affectactivity levels though there is no directevidence to support this relation (Buchanan,Eccles, & Becker, 1992). It is important torealize that hormonal pubertal processes area process rather than an event (Petersen,1987). That is, pubertal changes areoccurring over a long time span. Thus, toreturn to our opening example, there is nosudden hormonal event that would leadadolescents to suddenly feel tired.

The timing of puberty

Due to the tremendous individual variationin timing of the onset of puberty, the termsÒadolescentÓ and ÒteenÓ are notsynonymous. Information on the timing ofonset of puberty mostly stems from studieson girlsÕ menarche, i.e., the first indicationof a menstrual cycle (Tanner, 1975).Although menarche can be used as a markerfor the onset of puberty in girls, there is nosimilar marker in boys. Since the age ofmenarche (i.e., a girlÕs first period) can beeasily quantified, researchers tend to focuson this variable and assume the onset ofboysÕ pubertal patterns are similar. Usingmenarche as a marker, studies have shown adrop in the average age of puberty since theturn of the century (Marshall & Tanner,1986). This variation in timing has beenlinked to several causes: heredity,improvements in nutrition, familyenvironment and stressful life events(Belsky, Steinberg &, Draper, 1991; Frisch,1974; 1990; Graber, Brooks-Gunn &Warren, 1995; Steinberg, 1989; Surbey,1990). According to Frisch (1974; 1990),the improved nutrition in industrializedcountries, along with studies showing thatlow fat levels leads to cessation of themenstrual cycle strongly suggests thatnutritional improvements have caused thetrend toward earlier puberty. Alternatively,Steinberg (1989) has suggested the trendtowards earlier puberty could just as easilybe a result of stress factors related toindustrialization. Marital conflict and/orfather absence (Belsky, Steinberg & Draper,1991; Surbey, 1990) have also beenimplicated as stressors affecting the onset ofmenarche. Studies have shown that girlsraised without fathers and from divorcedfamilies do tend to mature earlier than girlsraised in intact families (Surbey, 1990).

Although causal factors are still underinvestigation, the implications of this trendhave generated much research. A centuryago, it was common to marry in the late teenyears with the onset of puberty occurringaround 16 years of age (Lancaster &Hamburg, 1986). Therefore, marital age andthe ability to reproduce were in harmony.Today, adults marry at a much later agewhile the average age of menarche in theUnited States has dropped to 12.8 years(Belsky, Steinberg, & Draper, 1991). Thus,adolescents are reproductively capable longbefore they are ready to marry and raise afamily. Because of this, the trend towardsan earlier onset of puberty has beenimplicated in the rise in school agepregnancies. There is a substantial amountof literature on the effects of earlier pubertyon the rise in school-age pregnancies thatwill not be covered in this summation ofgeneral adolescent behaviors (e.g. Lancaster& Hamburg, 1986).

The current adolescent experience onaverage

According to the empirical literature,adolescent development is basically apositive as well as successful experience formost adolescents (Graber & Brooks-Gunn,1996; Petersen, Richmond, & Leffert, 1993).Perhaps, many adults and parents viewadolescence and puberty as having negativeramifications because of the attention placedon those adolescents who evidenceproblematic behaviors (Petersen, Richmond,& Leffert, 1993). Yet, the processesinvolved in the development of thesesocially problematic behaviors, as well asthe groups of adolescents involved, arefundamentally different (Graber & Brooks-Gunn, 1996). In most adolescents, alongwith increasing size and reproductivematurity, come increasing cognitive abilitiesand knowledge which lead to a developing

understanding of self and others and anincreased ability to relate with others(Petersen, Richmond, & Leffert, 1993).Although encompassing tremendousindividual variation, most psychologistsrecognize adolescence as a positive time oftransition (Graber & Brooks-Gunn, 1996;Rutter, 1994). In fact, Cornwell andcolleagues (1996) suggest todayÕsadolescents are really more advantaged thanin the past. Declining fertility rates andpoverty, along with increases in parentaleducation have really led to positive changeswithin the family for the majority of todayÕsyouth (Cornwell, Eggebeen, & Meschke,1996). In general, the current view is thatthe majority of adolescents have noproblem coping with either the pubertalchanges or the transition (Buchanan, Eccles,& Becker, 1992).

Parent-adolescent conflict

Research has certainly documented someconflict in the parent-child relationshipduring puberty (Steinberg, 1981; 1989)though not necessarily as negativelyconflictual as portrayed in the popularliterature. Generally, most adolescents feelparentsÕ rules are fair (Achenbach &Edelbrock, 1981; Smetana, 1989). Studentsin my large freshman university class onfamily issues were asked whether they feltgoing through puberty was a rough time intheir lives, if they felt their parents wereunfair or if there was increasing conflictduring this time period. Most responseswere negative. Students shared that theywere happy that parents gave them clearboundaries as adolescents. They all statedthey would apply the same rules whenraising their own children.

Montemayor (1986) and Smetana (1988,1989) also believe that most conflicts areminor and result from the family

reorganization that occurs as children turninto adults. Smetana (1988, 1989) andMolina and Chassin (1996) have bothhypothesized that as adolescents mature,they may demand more autonomy,temporarily causing a redefinition of familyexpectations and regulations. If this is true,and if adolescents from divorced familieshave more autonomy (as suggested byHetherington, 1989), then there should bemore parent-adolescent conflict in intactfamilies than in divorced families. Smetana(1991) did find that there was less conflict inmother-custody families as compared tointact families. In both types of families,parent-adolescent conflict was related to thesame issues, usually the everyday details offamily life: interpersonal relationships,regulating activities, homework and severalothers. However, as Smetana (1991)points out, lack of conflict can also meanlack of communication. So, the autonomyhypothesis is still unresolved. Molina andChassin (1996) have recently found lessconflict in Hispanic families as boys reachedpuberty and suggest that puberty leads tocloser relationships within Hispanicfamilies, at least for boys. But since thesample consisted of alcoholic families, itcould be lack of communication that againleads to what appears to be nonconflictualrelationships. Again, all these effectswould still point to interpersonalrelationships within social contexts duringpuberty and not solely hormones or puberty(see Greene & Larson, 1991).

Enjoying the biological changes ofadolescence

Perhaps the secret to enjoying the biologicalchanges of adolescence is to ignore some ofthe popular literature on raising teens,especially when it is telling you to acceptÒself-centered, know-it-all, angry, criticaland impulsive behaviorsÓ as normal for

teenagers. Hormones should not be seen asa cause or an excuse for unacceptablebehaviors, and parents and/or youthprofessionals wishing to enjoy theiradolescents should not excuse anyunacceptable behaviors as inevitable.Overall, parents as well as youthprofessionals do need to allow increasingamounts of autonomy during thisadjustment period (Smetana, 1991). Yet,Smetana and Asquith (1994) did find thatboth adolescents and parents agreed thatparents should retain authority in thehousehold. Shifts in authority need to be inareas of personal jurisdiction. The problemis that adults and adolescents define personaljurisdiction differently. For example,parents see ÒpersonalÓ as pertaining to areasthat have only consequences to theadolescent. For parents, areas that have todo with social or moral rules are no longerpersonal and are subject to parentalauthority. Adolescents believe decisions insome of these areas are personal. Shiftingand setting these new boundaries within thefamily are part of the process of adolescentdevelopment. Each family will differ ondetermining how and when to shift theseboundaries. One example would be theadolescent who prefers being with friendsrather than attending the family picnic.Another example might be an adolescentwho feels her parents cross the personalboundary in attempting to choose herfriends. Professionals working with youthwill find adolescents often attempting todelineate these same boundaries. Forexample, although an adolescent might feeltheir choice of friends is their own personalbusiness, most adults would feel obligated tointervene when the friends of adolescentsuse alcohol or drugs. Although mostadolescents think parents have no right tocomment on personal issues such as style ofclothes, most adolescents also regardparental directives on moral issues and

behaviors as reasonable (Smetana, 1994).This indicates youth who hold an adult inhigh esteem would regard information onmoral issues and behaviors as reasonableinput. There are no simple answers orresolutions as adolescents turn into adultsand learn to make these decisions.

Although there is no such thing as a typicaladolescent or typical family, in general,parents are expected to impose authority thefirst six years of a childÕs life (Baumrind,1996). Somewhere around school age,children begin to understand that individualsare allowed to have different perspectivesbut at this age children still actively solicitadult approval. As children approachadolescence they need to form their ownidentity and become autonomous. Parentswho have provided explanations, andreasoned with their children as theydeveloped, have caused their children tointernalize parental values. By adolescence,these children are usually capable of reasonand able to consider the opinions of others.If parents have been firm about values andrules in early childhood, less rules areneeded and parents as well as other adultsshould be able to relax and enjoy watchingchildren emerge into adults. This is notquite the same as the implication of popularliterature (e.g. Caissy, 1994) which suggeststhat adults should be willing toaccommodate to adolescentsÕ moods andneeds.

Many years ago, Winnicott (1960) came upwith the concept of Ògood enoughmotheringÓ that Sandra Scarr (1992) hasrecently renewed as Ògood enoughparenting.Ó Believing there are no typicalfamilies or parents, Scarr has suggested thatchances are pretty good that unless thefamily or parents are considerably outsidethe ÒnormÓ, they will not ruin their childrenwith their parenting style. Although some

may not accept ScarrÕs conclusions andconsider them controversial, this adviceappears to make sense since it allowsparents

to trust their judgement with theirexpectations for what they deem reasonableand acceptable behavior for adolescents.Most adolescents are not victims of theirhormones. Adolescents are in fact changinginto adults and trying to learn to accept theresponsibilities of adulthood. They look toadults and parents to treat them with respectfor their emerging capacities but they alsoneed guidance. This guidance could beespecially critical in relation to ramificationsof the trend towards earlier pubertalmaturation which is experienced by thecurrent generation of adolescents.

Baumrind (1996) recently offeredsuggestions on how to effectively parentwhich can be related to all adults workingwith todayÕs youth. Baumrind states adultsshould focus on the optimal outcomeexpected for youth today. Three generalgoals usually strived for are character,competence, and communion. Adolescentswith character would be responsible,persistent and able to delay gratification. Tobe competent, adolescents should beeffective at human functioning, e.g., able tosupport and take care of themselves.Adolescents should also be able to relatewith others i.e., communion. Adults whochoose these goals for adolescents wouldprobably not accept self-centered,egocentric, angry, critical or impulsivebehaviors from adolescents as a ÒnormalÓresult of puberty and hormonal maturation,and rightly so.

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The author wishes to acknowledge andthank Ramona Carlos, ResearchAssociate at the 4-H Center andcolleague, for her insightful input indiscussions of this topic, as well as herediting comments on earlier drafts ofthis paper.