Neurobiology of Violent and Aggressive Behavior

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Neurobiology of Violent and Aggressive Behavior

• Andria Simpson
• Psych 346

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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

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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.

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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

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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

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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

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Medical Disorders Involving Aggressive and
Violent Behaviors

• Hyperthyroidism
• Cushings syndrome
• AIDS
• brain tumors
• Alzheimers disease
• Multiple Sclerosis
• Parkinsons disease
• Vitamin B12 deficiency
• hypoxia
• electrolyte imbalances
• hypoglycemia (controversial)
• Premenstrual Syndrome (PMS) (controversial)

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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

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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

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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.

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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.

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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.

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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.

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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 ones arousal as well as ones 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.

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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.

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• 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 (CrPCr) were lower in
  both the PFC and the AHC
• NAA is used as a nonspecific marker of neuronal
  density and CrPCr 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

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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.

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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)
• SSRIs
• Lithium Carbonate
• Beta adrenergic blockers
• Anticonvulsants

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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)

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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

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SSRIs

• 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 SSRIs, which is a side effect
  involving agitation and restlessness

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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

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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 arent observed for 4-8weeks
• cannot be used in patients with obstructive
  pulmonary disease, hypertension, congestive heart
  failure, or asthma

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Anticolvulsants

• Some anticonvulsants are good for treating
  aggressive behaviors pertaining to temporal lobe
  epilepsy because it has been found by studies
  using EEGs 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

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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.