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Neurobiology of Violent and Aggressive Behaviour

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					Neurobiology of Violent and
  Aggressive Behavior
        Andria Simpson
          Psych 346
               Overview
   Definition
   Introduction and brief overview
   Predictors of aggression and violence
   Related psychological and medical disorders
   Drugs and violence
   Research studies and findings (brain regions,
    neurotransmitters, hormones, and drugs
    involved)
   Pharmacological treatments
   conclusion
    Violence and Aggression
 Aggression is an act done deliberately,
  causing physical or mental harm on
  others. Can be either adaptive or non
  adaptive.
 Violence is a subset of aggression
  characterized by the undeserved
  infliction of physical injury.
              Introduction
   There are many risk factors involved in aggressive and
    violent behavior, making some people at a higher
    predisposition to display these behaviors.
   Temporal lobe has been implicated to be involved in
    aggressive and violent behavior. More specifically, the
    amygdala of the medial temporal lobe.
   Frontal lobe is also involved in violent and aggressive
    behavior
   Altered serotonin, GABA, norepinephrine, and dopamine
    levels may affect aggression. These altered levels of
    neurotransmitters can be due to psychological disorders
    or may be the cause of the symptoms of disorders.
   Drugs can influence aggressive behavior. (cause or
    result?) Drugs act on different regions of the brain
    affecting the information processing of these areas.
   Mentally handicapped individuals have a 5-25 times
    increased risk of committing a violent crime
Predictors of Aggressive and
      Violent Behavior
   An episode of loss of control or a pattern of violent
    behavior in the past* (primary risk factor)
   Chronic anger, hostility or resentment towards others
    and authority
   Get pleasure out of watching others be harmed or
    pleasure of out inflicting harm on themselves or
    others
   Lack of compassion and love (in and out of the home
    environment)
   View themselves as a victim
   History of childhood abuse or death of a loved one
   History of arson, bedwetting, cruelty to animals, and
    reckless driving
Psychological Disorders Related
  to Violence and Aggression
   In the DSM-III-R 19 disorders contained symptoms of
    aggressive behaviors, some of which are:
   Schizophrenia (due to the agitation and paranoid
    thoughts)
   Psychotic depression
   PTSD (due to hyperarousal of autonomic nervous system
    and nature of the trauma in the first place)
   ADD in both adults and children (impulse control problems
    may lead to aggressive and violent behavior)
   conduct disorder and oppositional defiant disorder (loss of
    impulse control)
   Dementia in the elderly (due to loss of impulse control)
   Mental retardation (due to loss of impulse control)
   Intermittent Explosive Disorder (IED) includes symptoms
    that are almost totally aggressive in nature
  Medical Disorders Involving
Aggressive and Violent Behaviors
   Hyperthyroidism
   Cushing’s syndrome
   AIDS
   brain tumors
   Alzheimer’s disease
   Multiple Sclerosis
   Parkinson’s disease
   Vitamin B12 deficiency
   hypoxia
   electrolyte imbalances
   hypoglycemia (controversial)
   Premenstrual Syndrome (PMS) (controversial)
Psychoactive Drugs and Violence
   Many drugs, when abused can lead to violence due to
    their action on the brain areas. For example:
   alcohol as well as alcohol withdrawal
   Benzodiazepines (can increase or decrease aggression)
   Amphetamines
   Cocaine
   Stimulants
   PCP
   hallucinogens
   Anabolic Steroids
   Opiate withdrawal
   many drugs cause a loss of control or lack of
    judgement within the user which is linked to the frontal
    lobe
Regions of the Brain Involved
 in Aggression and Violence
   Not all researchers agree on the anatomical positions in
    the brain where violent behaviors originate but the
    most common belief is in the hypothalamus, medial
    temporal cortex (amygdaloid complex of the limbic
    system), and the orbital frontal cortex.
   Mentally handicapped individuals may experience
    involuntary aggression and acts of violence, which may
    be due to dysfunction's present in the frontal lobe.
   Frontal lobes are used for the planning and execution
    of behaviors. Damage to the orbitofrontal cortex tends
    to display decreased impulse control in an individual,
    thus possibly leading to aggressive behaviors
                   continued
   damage to the orbitofrontal lobe can cause increased
    outbursts of anger and aggression and may not realize
    the consequences of their actions.
   In monkeys, when an amygdaloidectomy was
    performed, they showed no fear when in the presence
    of adverse stimuli (snakes).
   It has been proposed that the proper function of both
    the amygdala and orbitofrontal cortex may be needed
    for proper impulse control of violent behavior.
Neurotransmitters involved in
  violence and aggression
    Altered levels of serotonin,
     norepinephrine, dopamine, and GABA
     may be involved in aggression and
     violence. We will focus mainly of
     serotonin and norepinephrine.
                  Serotonin
   Decreased levels of serotonin may be involved in
    aggressive behavior. The lower levels of serotonin
    seem to cause increased levels of aggression.
   The CSF level of serotonin metabolite 5-
    hydroxyindoleacetic acid (5-HIAA) is a way to
    indirectly measure the level of serotonin in the brain.
   In some studies, a decreased 5-HIAA reading were
    found in certain subtypes of aggressive peoples. In
    alcoholic violent offenders, a decreased level was
    found; as well as in men who murdered an intimate
    partner as opposed to an acquaintance.
                 continued
   Decreased serotonin levels may be linked to an
    “impulsive” aggression subtype.
   Stimulation of the serotonin 1A, 1B, and 2 receptors
    tends to decrease aggressive tendencies.
   In addition to impulsive violence, serotonin may play
    a role in planned violence where the serotonin levels
    have been found to be higher than control subjects.
           Norepinephrine
   Increased NE seems to increase aggressive
    behaviors.
   A correlation between NE metabolite MHPG in the
    blood and an aggressive history has been found.
   NE increases one’s arousal as well as one’s level of
    awareness of the surrounding environment, which
    could further prepare a person to react aggressively
    to adverse stimuli.
   When NE and serotonin levels were both taken into
    account for aggressive behaviors, serotonin was
    found to play a greater role in the increased
    aggressive behaviors.
Research and Important Findings
   Filley et al. (2001) found that violent behavior may
    be due to dysfunctions in the brain but environmental
    and evolutionary factors are also involved
   Animal studies have found that lesions in the
    prefrontal cortex may increase aggression, while
    lesions in the amygdala may decrease aggression
   In human studies, damage to the
    orbitofrontal/ventromedial regions has been found to
    cause increased aggression and violent behavior
   EEG studies have shown abnormalities in the frontal
    region and the temporal region of the brain in repeat
    violent offenders compared to non repeat offenders.
   A study by Hugo et al. (2000) used magnetic resonance
    spectroscopy (MRS) to monitor concentrations of different
    compounds in the prefrontal cortex (PFC), amygdalo-
    hippocampal complex (AHC), and severity as well as
    violence in patients with mild mental retardation
   the concentrations of N-acetyl asparate (NAA), creatine
    phosphocreatine (Cr+PCr) were lower in both the PFC and
    the AHC
   NAA is used as a nonspecific marker of neuronal density
    and Cr+PCr is involved in metabolism in the brain.
   This information shows that there is decreased neuronal
    density in the PFC and AHC, as well as decreased
    metabolism in these regions in the patients with mild
    mental retardation in comparison to the controls.
   These findings however need to be further tested with a
    larger sample size as well as with other violent
    populations to find if they generalize to others or are
    specific to the mentally retarded
    PET Studies and Brain
         Activation
 PET studies have been used to analyze
  the brain blood flow and metabolism.
  Impulsive violent offenders were
  compared to a control group.
 Frontal and medial temporal lobe
  activation was associated with
  increased aggressive thoughts, initiation
  of anger, and violent criminal activity.
                 Treatments
   Not any specific treatment
   A high dose of almost any of the following drugs
    make aggression and violence fairly easy to suppress
    due to the sedative effects.
   Antipsychotics/Neuroleptics
   Anxiolytics (e.g.. Benzodiazepines)
   SSRI’s
   Lithium Carbonate
   Beta adrenergic blockers
   Anticonvulsants
    Antipsychotics/Neuroleptics
   work by binding to dopamine receptors as an antagonist
   have sedative effects to calm agitation and aggression
   Dose has to be high enough to suppress most motor
    activity (animal models)
   Not suitable for short-term suppression. Found to cause
    akathisia and hypotension in humans
   effective for treating long term aggression
   Effective for schizophrenia symptoms of aggression. Also
    used in acute mania, mental retardation, head injuries,
    and conduct disorder in children to reduce aggression
    and violence.
   Some patients do not respond at all or only partially see
    improvements
   Side effects: rigidity, akinesia, agitation (occasionally)
               Anxiolytics (e.g..
               Benzodiazepines)
   Suitable as a short-term sedative
   low doses increase aggressive behaviors and higher doses
    decrease aggressive behaviors in a rodent study
   withdrawal from repeated administration of
    benzodiazepines caused increased rates of aggression in
    animals
   as a sedative in humans, benzodiazepines reduce agitation
   benzodiazepines are fairly good for decreasing aggression
    in a variety of psychiatric disorders
   however, anti-anxiety effects can lead to disinhibited fear,
    resulting in increased aggression (occasionally)
   not good for long term use due to the addictive nature of
    these drugs
                      SSRI’s
   Reduces impulsive anger, irritability, and aggression
    in clinical patients
   good for controlling IED
   good for controlling aggression as a result of
    obsessive anxiety
   effective for controlling aggressive behaviors unipolar
    patients, and schizophrenics
   episodes of increased aggression can occur as a
    response to SSRI’s, which is a side effect involving
    agitation and restlessness
            Lithium Carbonate
   Works in three ways: increases serotonin synthesis,
    down-regulates beta-adrenergic receptors, and blocks
    dopamine receptors
   In Bipolar-II disorder, lithium carbonate is good for the
    treatment of aggression in hypomania with an “angry,
    paranoid” subtype
   good for the treatment of aggressive behavior that is not
    related to either Bipolar disorders
   good for IED and PTSD aggressive episodes
   Antisocial Personality Disorder with serotonin
    dysregulation and aggressive tendencies are well
    regulated with the treatment of lithium carbonate
   aggression due to ADD, mental retardation, and head
    injury can be decreased with this treatment
   used to control aggression in those without psychological
    disorders
     Beta Adrenergic Blockers
   Useful to regulate the increased norepinephrine
    metabolite MHPG
   in violent people, it decreases NE to decrease
    aggressive behaviors
   may work in the brain, on muscle receptors (as a
    relaxant) or both
   good to treat traumatic brain injury, PTSD, ADD,
    autism, and dementia patients with aggression
   beneficial results aren’t observed for 4-8weeks
   cannot be used in patients with obstructive
    pulmonary disease, hypertension, congestive heart
    failure, or asthma
            Anticolvulsants
   Some anticonvulsants are good for treating
    aggressive behaviors pertaining to temporal lobe
    epilepsy because it has been found by studies using
    EEG’s that epilepsy is related to aggression
   useful in temporal dysfunction due to head trauma
    and involves aggression
   useful to treat anger, aggression and IED
   anti-manic effects stabilize patients moods, thus
    leading to decreased aggressive and violent
    behaviors
                 Conclusions
   Violent and aggressive behaviors are associated with
    the orbitofrontal lobe, prefrontal cortex, and medial
    temporal lobe (amygdala). The frontal lobe is
    involved in decision making and executing behaviors.
    This may be why a lesion to this area can cause
    violent behaviors because a lack of control of their
    behaviors.
   Decreased serotonin levels and increased
    norepinephrine are correlated with aggression and
    violent behavior.
   There are many treatments available but not any
    specific one is the best. It depends on the specific
    symptoms of individual cases.

				
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posted:4/9/2010
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