Everything you need to know about the Teen Brain

The adolescent brain is best described as a work in progress. Our brains are about 90-95% of their maximum size by the time we are 6 years old, but they are definitely not finished changing! Massive changes continue to occur over the next 15-20 years, as connections within the brain are strengthened and refined. Adolescent brain development can be divided into three processes: proliferation, pruning and myelination.

1. Everything you need toknowaboutthe TeenBrain to

know

about

the

Teen

Brain

2. Significant brain growthand developmentoccurs
duringadolescence andcontinuesintothetwenties during

adolescence
,
and

continues

into

the

twenties
.
Some studies show that this growth and
developmentextendstotheageof30!
(Sowell et al., 1999; Sowell et al., 2001)
development

extends

to

the

age

of

30!

3. Adolescentbraindevelopmentcanbedivided Adolescent

brain

development

can

be

divided

into three processes:
•Proliferation(rapid growth of brain matter and the
formation of new connections within the brain)
•Pruning(cutting away of unused or unimportant
ti )
connec
ti
ons
)
•Myelination(insulating of brain pathways to
make them faster and more stable
)
(Sowell et al., 1999; Sowell et al., 2001)
)

4. Proliferation
:Totalbrainvolume
Proliferation
:

Total

brain

volume
By
age 6
, the brain is
about 95% of its
maximum size. Itreachesitsmaximum
*
It

reaches

its

maximum

size at 11.5 years in
g
irls*
,
and at 14.5
y
ears
g
,
y
in boys*.
(Giedd et al., 1999)
*
Boysbrains are larger
(on average) than girls
bi
Lenroot & Giedd (2006)
b
ra
ins.

5. Remembe
r
…
Maximum brain size
does notmean
maximum brain
maturity!
The brain continues to
mature for at least
another 10 years.

6. Remembe
r
…
Andalthough
boys
And

although

boys
brains are anatomically
biggerthan
girls
brains,
bigger

than

girls
brains,

size is not
directly
related to intelligence.

7. Thetissueofthebraincanbedividedintotwo The

tissue

of

the

brain

can

be

divided

into

two

types of matter,
grey
and
white
. These
ti d t tdiff t t ti
ssues grow an
d
ma
t
ure a
t

diff
eren
t
ra
t
es.
White matter looks white tothenakedeye andis
Grey matter looks grey
to the naked eye. It is
f
to

the

naked

eye
,
and

is

made up of axons.
composed o
f
neuron cell
bodies, dendrites, and glial
cells cells
.

8. Grey matter is where all the
thinkinghappens Thisisyour thinking

happens
.
This

is

your

brain’s processing centre.
White matter, containing those
long axons, are like a super
highway. They transport
information to different parts
ofyourbrain of

your

brain
.
Photo credit (CC 2.0): facemepls
, MSVG

9. Proliferation
:GreyMatter
Proliferation
:

Grey

Matter
Gttdl G
rey ma
tt
er
d
eve
lops
quickly during childhood,
but slows during adolescence.
Grey matter volume peaks at a
g
e 11 in
g
irlsand at
g
g
age 13 in boys. Then, the volume of grey
Lenroot & Giedd (2006)
matter begins to decline.

10. Pruning:
GreyMatterMaturation
Pruning:
Grey

Matter

Maturation

The maturation of grey matter is best described asaconstant
“
pushandpull
”
New
as

a

constant

push

and

pull
.
New

pathways grow, while others are pruned back.

Pruning is greatly influenced by experience, so itreallyisacaseof
“
useitorloseit
”
!
it

really

is

a

case

of

use

it

or

lose

it
!


Thismakestheadolescentbrainextremely

This

makes

the

adolescent

brain

extremely

versatile
, and able to make changes
dependingonthedemandsoftheenvironment depending

on

the

demands

of

the

environment
.

11. Pruning:
GreyMatterMaturation
Pruning:
Grey

Matter

Maturation
The brain matures in a back
-
to
-
front pattern The frontal
The

brain

matures

in

a

back
-
to
-
front

pattern
.
The

frontal

& temporal lobes are the last to mature.
Remember:
the frontal lobe is the home of planning
Remember:
the

frontal

lobe

is

the

home

of

planning
,
organization, judgment, impulse control and reasoning!
ontal
ietal
mporal
Lenroot & Giedd (2006)
Fro
Par
Tem

12. Proliferation
and
Myelination
:Whitematter
Proliferation
and

Myelination
:

White

matter
White matter makes up
myelin
,
which insulates axons and
speeds up the communication
between neurons.
It develops continuously from birth onwards, with a slight increaseduringpuberty
*
increase

during

puberty
.
The increase occurs just after the peak in grey matter volume (around
*
peak

in

grey

matter

volume

(around

age 11 in
girls*
and around age 13
in
boys*
).
Lenroot & Giedd (2006)

13. Saythatagain?! Say

that

again?!
Teens show a consistent pattern
f
o
f
brain development.
White matter increases in a
roughly linear pattern. The
patternissimilarin different
Grey matter follows an upside-
down U shape. The pattern differs
accordingtobrainregion
pattern

is

similar

in

different

brain regions.
according

to

brain

region
.
White
Grey

14. The Teen Brain is in a
Constant State of Development
And some areas of the brain
tftththTh
ma
t
ure
f
as
t
er
th
an o
th
ers.
Th
e
areas of your brain associated
withreward motivation and with

reward
,
motivation
,
and

impulsivity matures early.
Photo credit (CC 2.0): Daniel Flower

15. The Teen Brain is in a
Constant State of Development Yourprefrontalcortex Your

prefrontal

cortex
,
which thinks about things
logically weighsthepros logically
,
weighs

the

pros

and cons, and restrains
y
ou matures later. This
ymeans teens can be more
prone to riskier and
impulsive behaviors, and
less likely to consider
consequencesthanan consequences

than

an

adult would be.
Photo credit (CC 2.0): Alaskan Dude

16. RiskandReward Risk

and

Reward
It’s notthat teens are stupid,
or have no control over their
own brain. Studies have shown that teens knowwhen they are engaging in risky behavior (like
unprotected sex, drinking, or
drugs). However they are more likely to think that the benefits of thosebehaviorsoutweighany those

behaviors

outweigh

any

potential harm.
Reyna & Farley (2007)
Photo credit (CC 2.0): winnifredxoxo

17. RiskandReward Risk

and

Reward
It’s important to take a step
backandrealizethatthoughnot back

and

realize

that

though

not

everyrisky choice will result in
harm
–
some will. It’s not
enough to know there’s risk, you
need to also understand the
consequences. It could impact the rest of your life in a really
Playing Russian Roulette
with one bullet is certainly
much safer than playing it
negative way.
much

safer

than

playing

it

with five. But should we
really be playing it at all?
Photo credit (CC 2.0): Andres Bastidas
Reyna & Farley (2007)

18. So how does the brain So how does the brain matureafter adolescence?
There is evidence that these
changes continue
WELL
f
a
f
ter the teenage years.
In a study of young adults, the frontal lobes showed
large
changesuptotheageof30!
showed
large
changes

up

to

the

age

of

30!
This suggests that frontal lobe maturation is
(Sowell et al., 1999; Sowell et al., 2001)
important for
adult cognition
.

19. What does all this mean?
It means huge advances
have been made in studies
of brain develo
p
ment.
p

20. BUT
it is difficult to figure out
BUT
…
it is difficult to figure out
exactly how these
structural
brain changes
relate to functional
changes
in cognition and behavior.

21. Hopefully, the answers to these questions will come these questions will come within the next few years.

22. References References
Giedd J N Blumenthal J Jeffries N O Castellanos FX Liu H Zijdenbos A Giedd
,
J
.
N
.,
Blumenthal
,
J
.,
Jeffries
,
N
.
O
.,
Castellanos
,
F
.
X
.,
Liu
,
H
.,
Zijdenbos
,
A
.,
Paus, T., Evans, A.C., Rapoport, J.L. 1999. Brain development during childhood and
adolescence: A longitudinal MRI study. Nature Neuroscience. 2: 861-863.
Lenroot, R.K., Giedd, J.N. 2006. Brain development in children and adolescents: Insights from anatomical magnetic resonance imaging. Neuroscience and Biobehavioral Reviews. 30: 718-729. Sowell, E.R., Thompson, P.M., Holmes, C.J., Jernigan, T.L., Toga, A.W. 1999. In vivo evidence for post-adolescent brain maturation in frontal and striatal regions. Nature Neuroscience 2: 859
-
861
Neuroscience
.
2:

859
-
861
.
Sowell, E.R., Thompson, P.M., Toga, A.W. 2001. Mapping continued brain growth and
gray matter density reduction in dorsal frontal cortex: Inverse relationships during
postadolescent brain maturation. The Journal of Neuroscience. 21: 8819-8829. Reyna V F and Farley F 2007 Is the teen brain too rational? Scientific American Reyna
,
V
.
F
.
and

Farley
,
F
.
2007
.
Is

the

teen

brain

too

rational?

Scientific
American

Mind. 17: 58-65

23. Sun Life Financial Chai
r
InAdolescentMentalHealth In

Adolescent

Mental

Health
For more information visit
WWW.TEENMENTALHEALTH.ORG