Monday, July 9, 2012

Adolescence: Biosocial Milestones

Around age 11, you're starting to wonder where your baby went and by 18 she has all but disappeared and turned into an adult - although perhaps a bit less mature and more impulsive.

Childhood ends and melts into adolescence with the onset of puberty. Puberty normally begins between the ages of 8 and 14. With girls you'll notice puberty when she starts to develop breasts, pubic hair makes its first appearance, and she goes through a growth spurt. This is followed by a widening of the hips, her first menstrual period (the technical term is menarche), more pubic hair (its final pattern), and full breast development. With boys, his testes will grow, pubic hair will make an appearance, his penis will grow, he will ejaculate for the first time (spermarche), facial hair will start to grow, he'll go through a growth spurt, his voice will deepen, and finally more pubic hair. The typical age of menarche (girls) is 12 years and 8 months; for boys the typical age of spermarche is a little before 13 years, so the two take place at about the same time.

Some of the biggest differences between boys and girls in puberty are visibly noticeable, a girl's growth spurt generally comes about 2 years before a boy's; she'll also grow breasts by about age 16 but he won't have facial hair until about age 18. In the internal differences, girls are really only a few months ahead of boys. 

Even though baby will finish growing and maturing about 4 years after the first signs of puberty, many people continue to add height in their late teens and early 20s - and most people continue to add fat and muscle.

Hormones are the true start of puberty even though they are invisible from the outside. They are natural chemicals in the bloodstream and they regulate everything from sleep to hunger, stress to sexual desire, mood to immunity. Hormones are regulated from deep within the brain, starting with the hypothalamus which sends signals to the pituitary, a gland also located inside the brain. The pituitary produces hormones which in turn stimulate the adrenal glands located above the kidneys to produce even more hormones. This trail is called the HPA axis, hypothalamus-pituitary-adrenal, and many of the hormones that regulate puberty.

Another sequence is called the HPG axis; hypothalamus-pituitary-gonad. The gonad is the sex gland, meaning this sequence has to do with the production of sex hormones. For girls, this means mostly estradiol, the chief estrogen; for boys, this means testosterone, the chief androgen. Of course, these are not the only sex hormones produced, just the main hormones produced. Testosterone levels in boys skyrockets, producing up to 20 times their prepubescent levels. Estradiol levels in girls increase compared to prepubescent levels, but not quite so much - only about 8 times.

As you can plainly see, hormone production has a serious effect on adolescents. Hormones flow through the bloodstream and cause sudden eruptions in emotions, causing quick emotional extremes, sexual desires and thoughts, anger for boys, and happiness, rage and depression for girls. Adults feel these same surges, but they are not as erratic or as powerful as they are for adolescents; in addition, added maturity and cognitive awareness make these surges easier to control in adults.

Probably the hardest part of controlling hormones for adolescents is the cycle of hormones and emotions. Hormones cause extreme emotions, which in turn produce hormones, which in turn intensify the emotion. So it is that situations with adolescents can quickly escalate - they don't even realize it but they quickly worsen an emotional situation given the chance.

There are a few variations in the onset of puberty. You might notice puberty in baby around age 11 or 12, but it can happen as early as age 8 or as late as 14. About one in 5000 experience precocious puberty, in other words, before age 8. The reasons are unknown. However, there are a few determiners for the age of onset. Genes, body fat, hormones, and stress all affect the age of onset.

Most of the variation in onset is genetic - monozygotic (identical) twins are very similar in the age of onset while half-siblings are less similar. However, these and other averages only apply to well-fed children. Wherever there are high rates of obesity, there will also be the earliest ages of puberty. The hormone leptin has also been identified as one of the triggers of puberty. The hormone affects appetite and generally the levels of leptin are very high at the onset of puberty. Leptin and body fat affect girls more than boys. Stress causes early onset of puberty,  for example, sick parents, divorce, or a violent neighborhood. One study found that girls who fight with their mothers and live with an unrelated man (i.e. stepfather) reached puberty earlier. Later in life, even the stress of traveling abroad can cause irregular menstrual cycles for women. Regardless of gender, malnutrition delays puberty.

Body image is a huge factor in nutritional deficiencies and one of the biggest challenges facing teens. Girls go on diets to get skinny so the boys will ask them out; boys want to look taller and stronger. Adolescents just aren't happy with their awkward, changing bodies. A common way to deal with body image is to take on an eating disorder. About 60% of teen girls and 30% of teen boys are trying to lose weight according to one survey, but almost in spite of this fact, about 13% of high-schoolers are obese and 16% more are overweight. Obesity is considered an eating disorder -  many kids start diets but quickly give up and give in, overeating and becoming lazy and flabby. Unfortunately, later in life these overweight and obese teens will be at a higher risk for diabetes, heart disease and stroke. At the other end of the spectrum, another eating disorder is anorexia nervosa. It is characterized by self-starvation and 5-20% of its victims eventually die of it - usually due to organ failure. Diagnosis of anorexia is made when: she (or he) refuses to maintain a body weight that is at least in the 85th percentile for height and age, she has an intense fear of gaining weight, there is a disturbed perception of her own body, denies the problem, and in the cases of women, she doesn't menstruate. Bulimia nervosa is similar in the distorted perception of self, but different from the self-starvation of anorexia. In bulimia, there is bingeing followed by purging either through vomiting or laxatives. The bulimic has an uncontrollable urge to overeat - usually thousands of calories within an hour or so. As a person with bulimia isn't starving herself, she is normally much closer to normal weight, but she does serious damage to the gastrointestinal systems and has a severe electrolyte imbalance.

One of the major challenges for adolescents lies in nutrition. These days, each generation is slightly less well-nourished than the previous; the healthiest diets are found among people over the age of 65. In 2007, a survey of high school seniors in the US found that only 19% ate five or more servings of fruits and veggies per day. 10 years prior, the same survey had found that 27% were getting the allotted daily amount. Iron deficiency is widespread - less than half of US teens consume the daily serving suggestion of iron because they pass up eggs and leafy greens for junk food. Calcium deficiency is rooted in the same problem, these days kids pass up milk for a cheaper soda. Studies have found a direct link between nutritional deficiencies and vending machines in schools. Another study found that 10- to 14-year-olds would probably choose healthy foods if they are priced more cheaply than junk food. Trouble is, a McDonald's salad costs four times the cost of a hamburger (in 2008 in NYC).

The growth spurt is a bit awkward as it starts in the extremities and works its way inward. Fingers and toes grow first, then hands and feet, arms and legs, and finally the torso catches up. You'll have advance warning for the growth spurt when suddenly the shoes you bought last week are a couple of sizes too small for her.

Bones lengthen and harden and children eat more and gain weight. Girls gain more fat than boys and by 17 girls have about twice the body fat percentage of her male counterparts. The weight gain comes first, then the height followed by muscles. An 18 year old boy has arms twice as strong as when he was 8 and he can throw a ball four times as far.

Organs also change during adolescence, after weight and height along with muscles. Lungs triple in weight, the heart doubles in size and beats more slowly, skin becomes more oily (causing acne), hair becomes courser and darker, and the lymphoid system (tonsils, adenoids, etc) decreases in size. The shrinking lymphoid system actually lessens the chances of catching colds or other respiratory diseases, and for this very reason asthma has been known to disappear during puberty.

The sexual changes during puberty are what really turn girls into women and boys into men. The primary sex characteristics - those directly involved in reproduction such as testes and ovaries - increase in size and mature in function. The secondary sex characteristics - those not directly involved in reproduction such as breasts and beards - also develop during puberty. Girls' hips widen and boys' shoulders become broad.

Sexual activity vary greatly depending on culture and religious beliefs. Certain cultures expect a girl to gain experience with someone her own age, others with a much older man and some with a younger man. Religious beliefs may promote celibacy until marriage, and depending on the adolescent they may choose to follow it. In the US in 2007, 62.4% of juniors in high school said they had had intercourse.

As for sleep - while many speculate that teenagers are just lazy because they stay up late and wake up even later - sleep is controlled by the hormones. Teenagers' hormones simply don't allow them to sleep early and they have a hard time waking up early. Sleep deprivation caused by staying up too late and being forced out of bed early for school is associated with insomnia, falling asleep while driving, distressing dreams, and mood disorders. Unfortunately, social policy doesn't take its cues from the hormones of teens. A study done on a high school in Minnesota who pushed their start time back from 7:25 a.m. to 8:30 a.m. After a year, 93% of parents and virtually all of the students approved of the change. Because of the change there were fewer tardies, absences, or disruptive or sick students, and the kids got higher grades.

One serious challenge among teenagers is accidental and violent deaths. Their impulsive behaviors lead to drug abuse and irrational decisions. Between the ages of 15 and 25, 46% of deaths result from accidents, 14% from homicide and 13% from suicide, not to mention adolescents have more injuries than any other age group.

Another hazard we don't often think of as hazardous to a teen's health is teen pregnancy. 83% of teen mothers in the US in 2005 were unwed, trying to raise their children alone. When an adolescent gets pregnant too soon, she complicates not only her pregnancy but her own growth. Teenage pregnancies have a higher risk of almost every complication related to pregnancy and the teen mother's hormones redirect from her own growth to sustaining a new life. Even if she gets an abortion, adolescents are more likely to have complications there. Baby born to an adolescent is less likely to be breast-fed and more likely later on to have poor health, inadequate education, low intelligence, and anger at society in general. Beside the risk of getting pregnant, sexual activity puts adolescents at risk for STIs (sexually transmitted infections). People between the ages of 15-25 only account for one-fourth of the sexually active population, but for one-half of all the STIs.

Perhaps the biggest challenge to adolescents is called generational forgetting, they do not learn from the generation before them. This leads to drug use, teen pregnancy, and a number of other problems simply because teens can be too hot-headed to listen to the advice of anyone older. Drug abuse particularly is a problem, even though it has decreased since 1976, marijuana users especially have much higher drop-out rates, unemployment rates, and they are more likely to become teenage parents than non-users.

While baby may not really be baby anymore at this point, it is of utmost importance to be patient with her. Don't rile her up - the hormone-emotion-hormone cycle will only make things worse - and you should encourage her to be religious or involved in the community to lessen her chances of becoming pregnant or a drug user.

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