A longitudinal study of reasons for smoking in adolescence

This longitudinal study examined factors related to smoking at age 13 and to persistence of smoking from ages 13 to 15 years in a sample (n = 719) of New Zealand adolescents. History of smoking at 9 and 11 years predicted smoking at 13 (odds ratio = 2.8), persistence of smoking from age 13 to 15 (OR = 2.4) and smoking at 15 among those not smoking at age 13 (OR = 2.4). While there were no significant sex differences in pre-adolescent and early adolescent smoking, by age 15 more girls than boys reported smoking. A concern with the immediate negative effects of smoking (taste, smell, feeling ill and feeling silly) as a reason for not smoking at age 13 was inversely related to smoking at age 15 (OR = 0.4). Reasons for smoking at age 13 were not associated with later smoking. Family disadvantage and use of alcohol and other drugs were also associated with later adolescent smoking.

Adolescence and sun protection

AIM

to examine adolescents' sun behaviours and use of sun protection measures, attitudes to tanning, and awareness of melanoma, in the light of the Cancer Society's Sun-smart campaign in the summer of 1990-1.

METHODS

a sample of 345 fourth formers from schools in Auckland, Wellington and Christchurch was surveyed regarding their experiences and beliefs about tanning, and their use of sun protection measures including sunblock lotions, hats and clothing; their knowledge of melanoma and risks for melanoma; and their exposure to the educational campaign and its message.

RESULTS

despite relatively high awareness of melanoma as a dangerous form of cancer, a significant proportion of the sample showed high positive attitudes towards tanning and high levels of sun exposure without adequate sun protection. On the positive side, reports of exposure to sources of information about melanoma were correlated with melanoma awareness, which in turn predicted use of sun protection measures.

CONCLUSION

the findings suggest that campaigns such as those of the Cancer Society have an important role to play in reducing high levels of sun exposure among adolescents. Continued efforts need to be directed at adolescents to increase the acceptability and use of sun protection measures.

Attention deficit disorder and age of onset of problem behaviors

In the course of a prospective longitudinal study, we examined age of onset of behavior problems in a group of boys and girls identified with attention deficit disorder (ADD) at age 11. Onset occurred during the preschool years, by the first year of schooling, or by the end of the second year of school. Onset was strongly related to informant source at age 11, pattern of comorbidity of disorder at age 11, and developmental language, perceptual motor, and IQ measures. Onset by the first year of schooling was particularly related to poor reading skills. By age 15, nearly three-quarters of those with onset of problems before age 6 had one or more DSM-III disorders.

Prevalence and correlates of the premenstrual syndrome in adolescence

In a longitudinal study of their health and development, 384 15-year-old females reported their experience of symptoms indicative of premenstrual syndrome (PMS). The prevalence of these symptoms is reported and a group of adolescents is identified with the syndrome (14%). PMS was associated with current self-reported anxiety, inattention, and poor health. Preadolescent self-report and maternal ratings of physical and mental health did not significantly predict adolescent PMS. The results suggest that the experience of PMS in adolescence may be mediated by perceived health status; the roles of mental health and maternal influence in the development of adolescent PMS may be minimal.

Sources of distress among New Zealand adolescents

This study examined sources of distress experienced by 15-year-old adolescents in a large sample from the general population. We identified four types of stressful life circumstances relating to problems of self-image and independence, academic and physical competence, parental conflict, and moving residence and schools. Girls reported higher levels of distress for the first three types of circumstance. Reports of distress were associated with poor family social support, maternal depression and parental separation. Both DSM-III disorder and poor social competence were associated with differential patterns of distress. Lastly, poor social competence and high distress were independent and additive predictors of mental health disorders.

Tracking relative weight in subjects studied longitudinally from ages 3 to 13 years

Heights and weights of a large sample of subjects studied longitudinally from ages 3 and 13 years were used to calculate relative weight, using a Body Mass Index score (BMI) which estimates adiposity. Males and females differed significantly in BMI scores only at ages 3 and 13 years. The correlations between BMI scores at all ages were positive and significant. The subjects were divided at each age into a 'light', an 'average' and a 'heavy' group based on the position of their BMI score relative to the 25th and 75th percentiles. Subjects were 'tracked' from ages 3, 7 and 11 years to determine whether they had remained in the same BMI group by age 13 years relative to their peers. Slightly fewer than half of the 3 year old subjects but the majority of 7 and 11 year old subjects remained in the same relative weight group by age 13 years. Only 1% of 7 and 11 year old subjects in the top and the bottom quartiles for BMI scores shifted from one extreme group to the other. Relative weight at 3, 7 and 11 years was more persistent for subjects with extreme bodyweights than subjects with bodyweights in the middle range. Consistent with the pattern of correlations, the tracking pattern for all 3 groups showed that subjects' BMI scores remained more stable as the subjects grew older.

DSM-III disorders from age 11 to age 15 years

Although research into the continuity of disorder from childhood to adolescence is sparse, results from both longitudinal and cross sectional studies suggest that the prevalence of disorder increases for girls but may remain more stable for boys. In this paper, the methodologies of two assessment phases of the Dunedin longitudinal study have been equated to estimate the continuity of DSM-III disorder from ages 11 to 15. Although the overall prevalence of disorder doubled between the ages, this was primarily because of an increase in nonaggressive conduct disorder and major depressive episode. The sex ratios in disorder had largely reversed from a male predominance at 11 to a female predominance at 15. In terms of persistence, over 40% of those with disorder at age 11 were also identified at age 15. However, over 80% of those identified with disorder at 15 did not have a history of disorder at 11. Significant sex differences were also found in the continuity of internalizing and externalizing disorders, with externalizing disorders showing more continuity for boys, and internalizing for girls. Logistic regression models were employed to evaluate the roles family background, academic and social competence, and early histories of behavior problems may play in the determination of disorder continuity.

Sleep problems in adolescence

A sample of 943 adolescents from the general population were questioned about sleep problems. A quarter of the sample reported needing a lot more sleep than they previously had, and 10% of the sample complained of difficulty falling asleep. Adolescents reporting sleep problems showed more anxious, depressed, inattentive, and conduct disorder behaviors than those who had no (or only occasional) sleep problems. Sleep problems, particularly multiple problems, were associated with DSM-III disorder. There were no significant differences between male and female adolescents on any of the above measures. Finally, sleep problems were relatively persistent over time from ages 13 to 15.

Indices of perinatal complications, family background, child rearing, and health as predictors of early cognitive and motor development

An index of adversity is a measure of risk that can be considered independently of individual risk factors. This study examined four areas of adversity in early childhood, namely perinatal complications, family background, child-rearing practices, and the child's physical health, and their relationship to developmental outcomes. Four indices of adversity in these areas were examined as predictors of cognitive ability and motor ability for 476 girls and 510 boys at age 5 years. Results of the study indicated that indices of family background and child-rearing practices were highly related to these developmental outcomes. An index of health problems was found to be significantly related to motor ability. The perinatal complications index was significantly related only to specific cognitive ability scores for boys. Previously, developmental outcomes have been assessed in terms of the magnitude of individual risk factors, but more effective screening procedures may need to take account of the additive effect of the number of relevant adverse risk factors.

Strict and inconsistent discipline in childhood: consequences for adolescent mental health

Recent reviews have suggested an association between discipline experienced in childhood and the development of later psychopathology. As part of a longitudinal study of the health and development of a large sample of New Zealand children, maternal reports of strict and inconsistent discipline were obtained when the sample members were aged 7 and 9 years. It was found that inconsistency was associated with early behaviour problems, but strictness was not. At age 15 years the prevalence of DSM-III disorders in the sample was established. Univariate analyses showed significant associations between inconsistency and low levels of strictness with externalizing disorder. Logistic regression analyses demonstrated that in the presence of other predictor variables including childhood problem behaviour, these associations only approached significance. However, when the two ratings were combined, rates of disorder for those who experienced more relaxed and inconsistent discipline were double the rates found in the sample remainder. No significant association was found between discipline and internalizing disorder.

Big cities, small towns and adolescent mental health in New Zealand

We examined the relationship between measures of mental health and residential locations with differing population densities in a large sample of New Zealand adolescents. There were no significant differences across residential locations in the prevalence of DSM-III disorders, poor social competence and level of help-seeking behaviours. However, adolescents from larger population centres reported more life event stresses. Those adolescents who experienced more frequent changes of residence were at risk for mental health problems.

Social competence in adolescence: preliminary findings from a longitudinal study of New Zealand 15-year-olds

Recently, there has been an increase of research interest in the nature of the relationship between the concept of "competence" and mental health and disorder. For a large sample of adolescents studied at ages 11 and 15 years, we developed indices of social competence at each age based on measures of social attachment and involvement in activities. There was a significant association between competence and "externalizing" disorders at both ages. Competence was related to "internalizing" disorder only at age 11. Preadolescent social competence did not predict later disorder at age 15 in the sample as a whole. However, externalizing disorder at age 15 was predicted by presence of disorder together with low social competence in preadolescence.

A twelve-year follow-up of preschool hyperactive children

Two percent (N = 21) of a large sample of preschool children were identified as "pervasively hyperactive." Compared with nonhyperactive preschoolers, these children more often came from families with high levels of adversity, and they showed poorer language skills. Over a 12-year follow-up period, the hyperactive preschoolers continued to show poorer cognitive skills, lower levels of reading ability, disruptive and inattentive behaviors at home and at school, and higher rates of DSM-III disorder in preadolescence and adolescence. By age 15, only one-quarter of this group were identified as having met "recovery" criteria. The findings point to the long-term adverse consequences of preschool hyperactivity and indicate the need for intervention with this type of disorder.

DSM-III disorders in a large sample of adolescents

The prevalence of DSM-III disorders was studied in 943 adolescents aged 15 years from a general population. Prevalence rates of disorder of 25.9% for girls and 18.2% for boys were found. The most prevalent disorders were overanxious disorder, nonaggressive conduct disorder, and simple phobia. Marked differences were noted among the disorders in terms of associated social competence, with multiple disorders and primarily "externalizing" disorders being related to poorer competence. A model of parental confirmation of disorder was developed suggesting that confirmation was more likely where the mother was depressed, the family low in social support, and the adolescent less socially competent.

Parent reports of disability among 13-year olds with DSM-III disorders

This study examined "physical" and "psychological" dimensions of disability associated with different DSM-III disorders in a large sample of 13-year old adolescents. The measure of disability was based upon the World Health Organization (1980) classification. We found that adolescents with multiple DSM-III disorders and those with attention deficit and anxiety disorders showed the highest levels of parent perceived disablement; depression and conduct disorder showed the least. In addition, adolescents with any kind of DSM-III disorder showed a rate of parent-reported hospitalization twice that of the remainder of the sample. They also had poorer perceived health, as suggested by lower parent and self health ratings than those without disorder.

Is there an association between lateral preference and delinquent behavior?

Results of recent research suggests an association between left lateral preference and delinquent behavior. In this study the lateral preferences of 881 seven-year-old children were determined using behavioral indicators of hand and foot use. Mixed-handedness was associated with parent-reported problem behavior scores and self-reported delinquency scores at ages 13 and 15. However, preference for left hand and foot use was found to be unrelated to the delinquency measures. The distribution of lateral preferences in an identified delinquent group was not significantly different from the distribution in the sample remainder. The lack of an association between left preference and delinquency may be accounted for by an increased cultural acceptance of individual preference.

Risk factors for behavioral and emotional disorder in preadolescent children

The relationship between risk factors and behavioral and emotional disorder was examined in 792 11-year-old children. Background characteristics such as sex, maternal depression, marital status of the parents, and reading problems distinguished between children with and without disorder. It also appeared that disorder was related to the number of risk factors experienced. This study, like others, failed to provide strong support for differences in background characteristics among children with different diagnoses. This may reflect the degree of overlap among disorders, because even children with only a single disorder may not be entirely free of the symptomatology of other disorders. For this reason it is important to assess children for multiple disorders or at least consider impaired functioning in other dimensions.

A 6 year follow-up of childhood enuresis: prevalence in adolescence and consequences for mental health

Recent studies have shown an association between enuresis and behavioural or emotional problems. The direction or causality of the association and its duration, however, remain unclear. This study followed a large group of children from ages 11 to 15 years and reported the prevalence of enuresis to age 13 years. The enuretic status of the sample at age 11 years was established relative to the history of enuresis at age 9 years. At age 11 years a significant association was found between enuresis and measures of psychopathology. This association was particularly evident for those children with secondary enuresis, and those who had a history of enuresis but had ceased to wet the bed. Current primary enuresis was not significantly associated with disorder. Similar associations were found between enuresis at age 11 and later disorder at age 13. At age 15 years no significant associations between enuresis and disorder were found. These findings have implications for parents of children with enuresis and for clinicians dealing with the disorder.

Is there an association between lateral preference and delinquent behavior?

Results of recent research suggests an association between left lateral preference and delinquent behavior. In this study the lateral preferences of 881 seven-year-old children were determined using behavioral indicators of hand and foot use. Mixed-handedness was associated with parent-reported problem behavior scores and self-reported delinquency scores at ages 13 and 15. However, preference for left hand and foot use was found to be unrelated to the delinquency measures. The distribution of lateral preferences in an identified delinquent group was not significantly different from the distribution in the sample remainder. The lack of an association between left preference and delinquency may be accounted for by an increased cultural acceptance of individual preference.

Markov, fractal, diffusion, and related models of ion channel gating. A comparison with experimental data from two ion channels

The gating kinetics of single-ion channels are generally modeled in terms of Markov processes with relatively small numbers of channel states. More recently, fractal (Liebovitch et al. 1987. Math. Biosci. 84:37-68) and diffusion (Millhauser et al. 1988. Proc. Natl. Acad. Sci. USA. 85:1502-1507) models of channel gating have been proposed. These models propose the existence of many similar conformational substrates of the channel protein, all of which contribute to the observed gating kinetics. It is important to determine whether or not Markov models provide the most accurate description of channel kinetics if progress is to be made in understanding the molecular events of channel gating. In this study six alternative classes of gating model are tested against experimental single-channel data. The single-channel data employed are from (a) delayed rectifier K+ channels of NG 108-15 cells and (b) locust muscle glutamate receptor channels. The models tested are (a) Markov, (b) fractal, (c) one-dimensional diffusion, (d) three-dimensional diffusion, (e) stretched exponential, and (f) expo-exponential. The models are compared by fitting the predicted distributions of channel open and closed times to those observed experimentally. The models are ranked in order of goodness-of-fit using a boot-strap resampling procedure. The results suggest that Markov models provide a markedly better description of the observed open and closed time distributions for both types of channel. This provides justification for the continued use of Markov models to explore channel gating mechanisms.

Determination of total (Na+ + K+)-ATPase activity of isolated or cultured cells

The aim of this work was to determine if the total (Na+ + K+)-ATPase of the plasma membrane of a cell population could be assayed without cell homogenization and partial purification of the enzyme. Several types of intact cells that were placed in an assay medium containing MgATP, Na+, and K+ hydrolyzed little or none of the added ATP. When the cells were pretreated with the ionophore alamethicin and then placed in the assay medium, they exhibited an ouabain-sensitive (Na+ + K+)-ATPase activity that increased and reached a limiting value with increasing alamethicin concentration. Since alamethicin did not increase the activity of the purified membrane-bound (Na+ + K+)-ATPase, its effects on the intact cells are probably due to the formation of large channels within the plasma membrane that allow the free access of the components of the assay medium to the intracellular domains of (Na+ + K+)-ATPase. Utilizing whole cells treated with alamethicin, total (Na+ + K+)-ATPase activity was determined in clonal pheochromocytoma cells (PC12), neuroblastoma x glioma hybrid cells (NG108-15), and myocytes isolated from adult and neonatal rat hearts. With the use of this whole-cell assay, the ouabain sensitivities of the enzymes in adult and neonatal rat heart myocytes were determined and found to be the same as those that have been determined with the use of partially purified enzymes.

Cognitive and social correlates of DSM-III disorders in preadolescent children

The relationships between some cognitive and social measures and the major syndromes found in a large preadolescent sample of children from the general population are described. The measures discriminated between disorder-no disorder for most variables examined and between the broad groups of externalizing and internalizing disorders, but not between individual diagnostic categories. An important exception was that ADDH and conduct disorder occurring as single disorders could be distinguished, but the frequent comorbidity of these and other disorders complicated many between-group comparisons.