Stress and biological response
Impact of uncontrollability and social evaluative elements
Meta-analysis review of 208 laboratory studies of acute psychological stressors
Dickerson SS and Kemeny ME 2004
Mean cortisol effect size for studies using cognitive tasks, public
speaking/verbal interaction tasks, public speaking/cognitive combination tasks, noise
exposure, and emotion induction. Public speaking/cognitive task combination yields the
Mean cortisol effect size for studies using passive tasks, motivated performance
tasks, uncontrollable motivated performance tasks, motivated performance tasks
with social-evaluative threat, and uncontrollable motivated performance tasks
with social-evaluative threat.
Mean ACTH and cortisol effect sizes for motivated
performance tasks with social-evaluative threat
and uncontrolability and for tasks without both
characteristics (ACTH =white column; cortisol=dark
• Impulsivity, "a force that moves something along" is a personality
trait which varies among individuals. Important for normal behavior
• Recent theories have decomposed impulsivity into 4 dimensions
which include urgency, lack of premeditation (the inability to
anticipate consequences), lack of perseverance (the inability to stick
to one's task) and Sensation-seeking (the experience positive
feelings towards risky actions).
• Abnormal impulse control is central feature of multiple mental health
• Impulsivity has been shown to be positively related to food intake.
As stated in the DSM-IV
Impulse control disorders include:
Intermittent explosive disorder
Impulse-control disorder not otherwise specified
The following ocnditions may have features that involve problems of impulse control:
antisocial personality disorder
• The essential feature of Impulse-control disorders is the
failure to resist an impulse, drive, or temptation to perform an
act that is harmful to the person or to others.
• Usually, the individual feels an increasing sense of tension or
arousal before committing the act and then experiences
pleasure, gratification, or relief at the time of committing the
• Following the act there may or may not be regret, selfreproach, or guilt.
• Excessive food intake has been positively linked with
How does Chronic Stress effects
• Pre-clinical and clinical studies have converged to show that
monoaminergic neurotransmitter systems (eg. dopamine) and the
cortico-striatal circuitry are essential to impulse control. Basically,
most evidence points toward that brain dopamine levels are
inversely related to impulsivity. Low activity dopamine states are
positively related to higher levels of impulsivity.
• Pre-clinical and clinical evidence shows that chronic stress and
resulting glucocorticoids affect the dopaminergic reward mesolimbic
pathway. Chronic stress leads to a state of low dopamine activity in
the brain and it has been observed to increase impulsivity. One of
the possible ways is through its effect on dopaminergic neurons
Dopamine Hypothesis of
• Postulates that the actions of drugs of
abuse are rewarding as a consequence of
activation of dopamine in the mesolimbic
• A similar mechanism occurs with
amphetamine, cocaine, nicotine and food.
Obesity and Brain Reward
Human dopamine projections:
(1) The nigrostriatal projection, which is concerned with movement .
(2) and (3) The mesolimbic dopamine projection, which is involved in rewardrelated functions.
Dopamine receptors and
(a) The upper pair of images
show dopamine receptor
availability in control and obese
participants. Note the clear
difference between them. The
lower pair of images show brain
metabolic activity. Note that
there is no difference between
(b) The relationship between
brain dopamine receptor
availability and the degree of
(Want GJ, Volkow ND et al 2001; Volkow ND and
Wise RA 2005)
What is the relationship between
Dopamine and Obesity?
• Obesity Song
– “What if you lack a
that would hold back
the feeling of rapture,
and here is the case
secretion, you are
more receptive to an