Adolescence: What, why and when?

What is adolescence?
      Adolescence is the transition from childhood to adulthood, a period during which an individual acquires the skills necessary to survive on his/her own away from their parents or other caregivers.  The age range during which this transition occurs can vary, but often encompasses the entire second decade of life or longer. 
      Adolescence can be a very confusing time for everyone involved.  Happy, fun-loving children can somehow morph into bitter malcontents in no time flat.  How do I know this?  Because I remember being one!  For some reason, many of my friends and colleagues have forgotten just how strange, confusing, exciting, frightening, exhilarating, etc., the adolescent years are.  Adolescence is a time of intense flux -- emotionally, behaviorally, and physically.  If one grabbed a copy of the DSM and examined the diagnostic criteria for adult psychopathologies, they would find that even normal adolescents exhibit symptoms that would be considered causes of concern if exhibited by adults.  Changes in sleep, diet, mood, weight, attitude, decreased pleasure from daily activities, and the list goes on, are all normal, and probably very adaptive, during adolescence.  If an adult rattled this list of behaviors off to their family doctor during a routine checkup, there is a good chance they would leave with a referral to a psychiatrist!
      As should be clear from the discussion below, much of the chaos that occurs during the adolescent years is both normal and necessary, regardless of how painful it can be for both parents and kids.  The image below highlights some of the take home messages from a recent meeting of the NY Academy of Sciences on the topic of adolescent development. We will explore some of these issues in this and subsequent sections.     

Why does this stage of development occur?
      Some animals must fend for themselves immediately after hatching from an egg or shortly after leaving the womb.  Being born prepared for independence has its pluses and minuses.  On the plus side, the animal does not require an extended period of nurturing and can immediately go out and find its own food.  It does not have to compete with siblings for the attention of the mother and can survive without adult help.  However, on the negative side, and there are some big negatives here, essentially all of the instructions that the animal is going to have to assist in its survival come with it into the world.  While it might be able to learn a new trick or two, it will not be able to roll with major changes in the environment.  If your brain tells you that you simply must eat green bugs and there are NO green bugs in the world, then you're in trouble!
      In stark contrast to that scenario, humans are born with an incredible ability to roll with changes in the demands of an environment.  While our brains have probably not changed at all in the past thousand years, the repertoire of skills necessary to survive certainly has.  Humans take these demands in stride.  Unfortunately, this flexibility comes at a great price -- we are born incredibly dependent on others.  Imagine a one month old, or even an 18 month old, human trying to survive by itself without support.  This trade off is clearly more than fair, or we would not have survived as long as we have. 
      An amazing amount of learning takes place during the first decade of life, a time period characterized by our dependence on adult caregivers.  During that time, we explore ourselves and our worlds using the family, or other caregivers, as a home base.  Eventually, in order for our species to survive another generation, we need to venture out away from the family, out into the deeper end of the gene pool, and create families of our owns.  That clearly can not happen overnight.  Most of us would not have made it had our parents just dropped us off at a bus stop when we were 10 and said, "Well, it's been great, now it's time for you to do this on your own!"  For humans, as for many other mammalian species, there is a transitional stage between childhood and adulthood.  That stage is adolescence.

When is adolescence?
      Adolescence does not have a distinct onset and offset. While it is possible to offer a rough beginning and a rough end, there are simply no absolute boundaries. This is true for rats, humans, and any other species that you could imagine studying. In general, as mentioned above, adolescence is considered a transition from childhood to adulthood, a period during which an individual acquires the skills necessary to survive on his/her own. It involves changes at numerous levels, some of which are defined biologically and some of which are defined behaviorally. In humans, some have suggested that adolescence encompasses the entire second decade of life (i.e., 10-20 years of age), while others suggest that 12-18 is a more conservative range (Spear, 2000a,b). In rats, adolescence is even trickier to define than in humans. A rough estimate of the age range for adolescence in rats is between 30-50 days of age (Little et al., 1996).
      As you can see, there is simply no fixed age range to define the boundaries of adolescence. In fact, the transition from childhood to adulthood could actually be extended or shortened depending on the individual and the demands placed on the individual by his/her surroundings. For example, in the United States , many college students remain dependent on their families and do not join the work force until after they graduate, which means that they technically remain adolescents into their early- or mid-20s. In contrast, in other countries, the individual might be required to work and provide for an entire family during their early teen years, thus forcing the transition to be complete at a much earlier age, closer to the completion of puberty. It is also important to recognize that, because adolescence is a period of development during which a multitude of changes are taking place, the onset and offset of adolescence is, in the end, determined by how it is operationally defined.
      In my opinion, if a time frame must be chosen, it is safest to consider that adolescence encompasses the entire second decade of life.  That is how the term will be used in this site.  Again, in the end, it is the collection of changes that truly defines adolescence, not the specific age range.

What are some of the basic changes that occur during adolescence?
      Linda Spear (2000a,b) has determined that there are several common themes in adolescence that humans share with other species, including rats.  Here are a few of those themes and a brief discussion of each.

An increase in time spent with peers and a decrease in time spent with one's family 
      Given total freedom, most teenagers would not choose to stay at home with their families, at least not for very long or often!  They would much prefer to IM their friends, talk on their cell phones with friends, page their friends, communicate via courier pigeon, etc.  I am certain it has always been this way for humans.  It is just far easier now to communicate around the clock than it ever has been.  The reason why this is adaptive should be obvious.  In order to jockey for position in the social hierarchy, find mates, acquire the skills necessary to compete with peers, form alliances with peers, etc., it is very important to spend time around one's peers.  Indeed, one could look at sports and other competitive play behavior, parties, and even just hanging out, as training or preparation for the social competition of adulthood.
      It certainly seems that being a teenager these days is very risky business, perhaps more so than in previous generations.  I am well aware that many parents feel the urge to simply prevent their kids from ever leaving the house.  While this might help ensure their safety, it can also put them at a terrible disadvantage socially.  They will eventually have to compete with their peers for mates, money, and other resources, and form social networks to help them succeed.  To use an analogy, watching basketball from the sidelines all day long is no substitute for playing the game.  Opting not to play the game, or being prevented from doing so, can make competing as an adult even more difficult. 

Increased risk-taking and exploration
       This is perhaps one of the most important and poorly
understood aspects of normal adolescent development.
If adolescents were perfectly content staying at home with
their families all of the time and had no desire to explore
the world, meet new people, etc., then they would never
venture into the deep end of the gene pool and the species
would quickly die out.  They simply must be driven to explore,
seek novelty, and take risks.  The repertoire of skills that an
individual needs to acquire during adolescence changes from
generation to generation.  It is critical to the survival of the
species that adolescents are willing to take chances, have
novel experiences, and learn new skills. 
      Risk-taking and novelty seeking can take some forms that
are hard to approve of or even comprehend.  As a graduate
student, I recall taking a break from studying for comprehensive
exams and walking to the window (a big mistake as it was a
nice spring day and I was stuck in the lab!).  Below the
window was a group of teenage boys taking turns rollerblading
as fast as they could, backwards, with no pads, down
several flights of very steep concrete steps.  Clearly, this was
probably not the best decision that any of them had ever
made and it could have had disastrous consequences. 
However, their behavior and all of the processes leading
up to it (e.g, decision-making, impulse control, risk-taking
and reward-seeking) were simply prime examples of what
takes place during adolescence.  As the quote on the right
captures, adolescence really is a unique stage with regard
to the kinds of decisions that people make and the risks
they are willing to take.
      Exploring altered states of consciousness through experimentation with substances is another common manifestation of risk taking and novelty seeking during adolescence.  As will be discussed in a subsequent section, more than 1/2 of all high school seniors have smoked marijuana and roughly 80% have consumed alcohol. Fortunately, the vast majority of adolescents do not engage in such activities regularly and do not go on to develop problems with substances. 
      One key message here is that adolescents are built to take risks and seek novel experiences.  Trying to prevent them from doing so is typically futile, as it is simply part of their biology. What we can do as parents, friends, and members of the community is to create opportunities for adolescents to take healthy risks (yes, there is such a thing) and reinforce them for doing so.  For instance, the data tell us that the more extracurriular activities that an adolescent is involved in, the less likely they are to drink heavily or do other substances. Creating opportunities for kids to explore and take some chances can minimize the likelihood that they choose less healthy, riskier options to satisfy their need to do so.  Not every parent can afford to let their child go sky diving, bungee jumping, or snowboarding.  However, what about finding a YMCA or community center with a basketball court that stays open late on the weekends?  Not every kid will want to take advantage of an opportunity like playing basketball on a Friday night, but some will.  The point is simply that there are things we can do to diminish the risks that adolescents take besides trying to force them to change their nature, which typically does not work and might be detrimental to their development.   

Increase in conflicts with authority, including parents
       This is essential for several reasons.  For one, as discussed above, adolescents must push away from their parents, and the parents must push the adolescent away from them to some extent, in order to propel the adolescent into the deeper end of the gene pool. If adolescence was characterized by a growing satisfaction with authority, this simply would not happen!
       Human are social animals.  Mating and obtaining resources involves competition.  Those at higher rungs on the social ladder enjoy better odds of mating and obtaining resources.  Jockeying for position in the hierarchy involves conflict.  For males, such conflict is typically more overt or physical.  Research indicates that, for females, such conflict is more likely to involve sabotaging social relationships, manipulating friendships, etc.  Regardless, an increase in conflict during adolescence, whether the conflict is with peers or authority, makes sense given the purpose of this stage of development.
       One of the key benefits of the adolescent period is that it allows the individual to acquire the skills necessary to succeed as an adult in the current environment.  These skills might differ from the skills that allowed one's parents to survive.  In other words, it is not necessarily healthy or adaptive for adolescents to take on all of the characteristics of the existing adults.  This would limit the true utility of the adolescent period with regard to our evolution as a species. A natural tendency to be in conflict with adults helps propel adolescents to find their own paths.  

Changes in sleep patterns, including a tendency to go to sleep later and wake up later
      I wish I had a good explanation for this one.  It probably is not adaptive or healthy in its own way.  It is probably a consequence of some other set of changes taking place in the body that is adaptive and healthy.  Regardless, the sleep patterns of teenagers can be fragmented and unfulfilling.  Many individuals, including some pediatricians, believe that schools should actually start later in the morning to accommodate the sleeping habits of a typical adolescent.

Puberty (sexual maturation)
       Puberty refers to a constellation of hormonal and physical changes that prepare the male and female bodies for procreation and physical confrontation (particularly males).  Puberty and adolescence overlap but are not the same thing.   

This transition can be particularly hard on healthy families!
        As the changes mentioned above suggest, evolution seems to have equipped us with a set of behavioral tendencies that helps aid the transition into adulthood.  At a very deep level, the adolescent is driven to push away from the family.  At the same time, many parents might feel driven to push back.  The closer the family, the harder this transition can be.  In the end, however, it has to happen.  If it did not, then our species simply would not survive.