Pubertal Timing Effects

A large body of literature involves studies examining links between pubertal timing and adjustment in adolescents, mainly because there is substantial variation among individuals regarding when puberty begins and how it progresses (Tanner, 1970). Girls typically exhibit the external manifestations of puberty about 1 or 2 years earlier than boys. Early-maturing girls can therefore develop 3 to 6 years ahead of boys as well as developing earlier than on-time or late-maturing girls. Variations in pubertal timing are most likely a combination of genetic differences and environmental factors such as nutrition, exercise, and health conditions.

Classifications of maturational timing may differ by study, even when the same pubertal status measure is used, such as the Tanner. Many studies group adolescents using population norms (Duke-Duncan, Ritter, Dornbusch, Gross, & Carlsmith, 1985) or classify adolescents according to sample distribution into early, on-time, and late developers. Researchers have typically considered the earliest 20% within the distribution for that sample as the "early" developers and the latest 20% as the "late" developers (Brooks-Gunn & Warren, 1985; Graber et al., 1996). Another method is to use sample values to indicate the deviation from the mean, such as defining more than one standard deviation above or below the group mean as the threshold for early or late pubertal maturation (Alsaker, 1992). Some researchers have used ratings of perceived pubertal timing, in which adolescents rate their timing as earlier, the same, or later than their peers (Dubas, Graber, & Petersen, 1991; Graber, Lewinsohn, Seeley, & Brooks-Gunn, 1997; Graber, Seeley, Brooks-Gunn, & Lewinsohn, 2003; Obeidallah, Brennan, Brooks-Gunn, & Earls, 2004). These varied methods result in cross-study variation in the maturational and chronological ages of adolescents classified in the same timing group. In the cases where the same classification system is used, different samples, having different distributions, may exhibit various percentages of off-time and on-time girls (even if same definition of timing is used). It is also important to consider that when assessing pubertal timing, studies often do not include a complete design, in that at any one grade level or age, a complete range of pubertal growth will not be seen, resulting in restricted ranges (Brooks-Gunn, Petersen, & Eichorn, 1985).

A few hypotheses have emerged to explain links between pubertal timing and psychological development. The "off-time" hypothesis is the most general one; it predicts that both earlier and later development in girls and boys compared to one's same-age, same-gender peers is a risk factor for problem behaviors (Caspi & Moffitt, 1991). A more specific hypothesis is the gendered "deviation" pattern of pubertal timing effects, where early maturation is a risk factor for females but late maturation is a risk factor for males. This hypothesis is based on the developmental pattern that girls, on average, mature earlier than boys. Girls who mature earlier than their peers or boys who mature later than their peers are considered to be in the "deviant" categories (Brooks-Gunn et al., 1985; Petersen & Taylor, 1980).

The "early maturation" hypothesis is also referred to as the "stage-termination" hypothesis (Petersen & Taylor, 1980). This hypothesis posits that early maturation is a risk factor for adjustment problems among both females and males across a range of outcomes (Brooks-Gunn et al., 1985; Caspi & Moffitt, 1991; Ge, Conger, & Elder, 1996; Tschann et al., 1994). Early maturation may be disadvantageous because early maturers experience social pressure to adopt more adult norms and engage in adult behaviors, even though they may not be socially, emotionally, or cognitively prepared (Brooks-Gunn et al., 1985; Caspi & Moffitt, 1991) for the new experiences. This hypothesis involves the notion of stage termination (Petersen & Taylor, 1980), which means that early maturation disrupts the normal course of development such that early maturers have less time and are less experienced to handle adult behaviors.

Effects of Pubertal Timing on Internalizing Symptoms

Early maturation has been repeatedly associated with more internalizing symptoms and psychological distress in girls, compared to on-time or later maturing peers (Brooks-Gunn et al., 1985; Ge et al., 1996; Graber et al., 1997; Graber et al., 2003; Hayward et al., 1997; Stattin & Magnusson, 1990). During early adolescence, girls begin to manifest higher levels of diagnosed depression and depressive symptoms than boys. By adulthood, rates of depression are approximately 2 to 3 times higher among women than men (Culbertson, 1997; Petersen et al., 1993). In a longitudinal study investigating links between pubertal transition and depressive symptoms in rural White youth living in Iowa, girls began to experience more depression than boys in the eighth grade and this difference persisted through mid- and late adolescence (Ge, Conger, & Elder, 2001a). Girls who experienced menarche at a younger age subsequently experienced a higher level of depressive symptoms than their on-time and late-maturing peers, at each annual assessment during the 6-year study. Additionally, the interaction between early menarche and recent life events predicted subsequent depressive symptoms for girls. Interestingly, the significant main effect of gender on depressive symptoms disappeared when pubertal transition, recent life events, and their interaction were included in models, suggesting that pubertal factors may explain a significant part of the observed gender differences in depressive symptoms during adolescence.

In one of the only studies that has examined long-term consequences of pubertal timing on psy-chopathology in young adults, young women who had been early maturers (based on self-reports of perceived timing relative to one's peers) continued to have higher lifetime prevalence rates of major depression, anxiety, disruptive behavior disorders, and hence any Axis I psychiatric disorder, as well as higher lifetime rates of attempted suicide in comparison to other women. The on-time and late maturers did not "catch up" in rates of disorder (at least by age 24), and differences in lifetime prevalence rates were maintained into adulthood (Graber et al., 2003).

On the other hand, in boys, findings on links between pubertal timing and internalizing symptoms are more inconsistent. Many of the earlier studies on pubertal timing in boys found that early-maturing boys were better off than their later-maturing counterparts, on measures of social, psychological, and behavioral outcomes (Jones, 1957, 1965; Mussen & Jones, 1957). Studies since the 1950s and 1960s have found more mixed effects. In the NIMH study of puberty and psychopathology, a higher rate of negative emotional tone has been found in late maturing boys in mid and late adolescence as compared to their agemates (Nottelmann et al., 1987). However, studies have also found that early-maturing boys experience more internalizing symptoms (Petersen & Crockett, 1985; Susman et al., 1991; Susman et al., 1985) or that both early- and late maturing boys show more depressive tendencies (Alsaker, 1992). Graber and colleagues (1997) found that late maturing boys experienced more internalizing symptoms than their on-time peers, and that both early- and late maturing boys showed significantly higher rates of depression than on-time maturing boys. In a longitudinal study with White boys living in a rural area, early-maturing boys, compared to their on-time and late-maturing peers, exhibited more internalized distress (Ge, Conger, & Elder, 2001b). Results from a large-scale study of African American boys also indicated that early-maturers reported higher levels of internalizing symptoms (Ge, Brody, Conger, & Simons, in press). In sum, more recent studies of pubertal timing in boys show a trend for early- and late-maturing boys to experience more internalizing symptoms than their on-time peers.

According to the early maturation, or stage-termination, hypothesis, if African American girls are indeed developing earlier than their White counterparts (they are the earliest to mature across ethnic groups), and thus should experience the most stress. So far a few studies have tested links between pubertal timing and adjustment across ethnic groups. While one study found associations between early menarche and depressive symptoms in White girls but not African American or Hispanic girls (Hayward, Gotlib, Schraedley, & Litt, 1999), another study including only African American children (N = 639), results showed that early maturing African American girls had higher rates of depressive symptoms (Ge et al., 2003). A study that examined pubertal timing effects across Latina, African American, and White children from economically diverse Chicago neighborhoods found that girls in each ethnic group who matured "off-time," that is, earlier or later than their same-age, same-gender peers, experienced more clinical levels of depression/anxiety, with strongest effects found in White girls (Foster & Brooks-Gunn, manuscript under review). It is important for researchers to further address associations between pubertal change and adjustment in non-White girls and boys, as this group has been understudied. It is possible that girls of different ethnic groups may differ from White children in theoretically important ways, such as in their preparation for puberty or in the responses from others within their ethnic group to their pubertal changes and attitudes about it.

Links Between Pubertal Timing and Externalizing Behaviors

Early maturation in girls has also been identified as a risk factor for externalizing behaviors. Studies show that early maturing girls tend to engage in risky behaviors, such as delinquency, earlier in adolescence and more frequently than their same-age peers (Caspi & Moffitt, 1991; Flannery, Rowe, & Gulley, 1993; Magnusson, Stattin, & Allen, 1985). Early maturing girls display more adverse outcomes if they had a history of behavior problems prior to puberty (Caspi & Moffitt, 1991) and have higher lifetime histories of disruptive behavior disorder in the high school years (Graber et al., 1997). Additionally, early-maturing girls show earlier onset and higher levels of substance abuse behaviors, such as cigarette smoking and alcohol drinking, compared to their on-time and late maturing age-mates (Aro & Taipale, 1987; Dick, Rose, Viken, & Kaprio, 2000; Magnusson et al., 1985). In the National Longitudinal Study of Adolescent Health, early-maturing girls in the seventh grade were three times more likely to be in the most advanced stage of substance use (involving alcohol use, drunkenness, cigarette use, and marijuana use) than the girls in the on-time/late group and in general, early developers were more likely to advance in substance use, regardless of their level at Grade 7 (Lanza & Collins, 2002). Early maturers show a higher current and lifetime prevalence for substance use (Graber et al., 1997), although other longitudinal data suggests that the association between early maturation and substance use holds only for girls whose advanced developmental status, relative to same-age peers, remained stable between the ages of 12 and 14 (Dick, Rose, Pulkkinen, & Kaprio, 2001).

For boys, the research on externalizing behaviors has mostly indicated effects for early maturers, or for both early- and late-maturing boys compared to their on-time peers. For example, both early- and late maturing boys have been found to have higher rates of delinquency than their on-time maturing peers (Williams & Dunlop, 1999). Early-maturing boys have been found to be at higher risk for early onset of sexual activity and tobacco and alcohol use (Graber et al., 1997; Kaltiala-Heino, Rimpela, Rissanen, & Rantanen, 2001; Wichstrom, 2001). On the other hand, in their examination of long-term consequences of pubertal timing, Graber and colleagues (2003) found that it was the late maturers, in comparison to other men, who had elevated onset of disruptive behavior and substance use disorders during the transition to adulthood.

In sum, early maturation is a consistent predictor to the onset of internalizing symptoms and externalizing behaviors in girls. Effects of both early and late maturation have been found for boys. Pubertal timing effects may be most pronounced during early adolescence and decrease during late adolescence (Weichold, Silbereisen, & Schmitt-Rodermund, 2003), although the literature on this point is rather limited. When inconsistencies in findings occur, possible reasons may be the different methods of measuring pubertal timing and the different ways of assessing outcome variables. It should be noted that the majority of research on pubertal timing has focused on its short-term consequences and more research on the long-term consequences is needed. Also, researchers should consider the duration of timing status, that is, how long adolescents remain consistently early or late, as one study has suggested that effects of timing were found only when interindividual differences in timing remained stable over adolescence (Dick et al., 2000).

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