13. Psychological Disorders Flashcards
Why are psychological disorders so difficult to define?
Because we don’t understand the underlying biological causes. Unlike physical disorders, we can’t match symptoms to exact causes, consequently we can’t find accurate treatments.
What is addiction?
A strong and harmful need to regularly have or do something. Can be substance related or activity related. It is compulsive engagement in rewarding stimuli, despite adverse consequences.
What do different addictions share in common?
They affect either dopamine or norepinephrine.
What are agonists and what are antagonists?
Agonists - drugs that occupy receptors and activate them.
Antagonists - drugs that occupy receptors but do not activate them.
What happens if an agonist and antagonist want to bind to the receptor at the same time?
There will be less activation
What is drug affinity?
The tendency to bind to a receptor
Different drugs have different affinity
Low affinity –> low tendency to bind to receptor (need higher concentrations of the drug to bind) vice versa
What is drug efficacy?
The tendency to activate receptor; level of activation after binding.
More ions can flow through –> higher efficacy
Why do people respond differently to drugs?
Different people have different types of receptors. The slight difference does not affect function, but they may affect drug affinity. We have a lot of variability across multiple molecules and proteins. Move towards individualised drugs for specific people.
Is a drug with high affinity, and low efficacy an antagonist or agonist?
Antagonist. Even though it binds, but activity is low. Fight for space with neurotransmitters.
What are the 3 ways can drugs affect synaptic activity?
1) Affect production of dopamine
2) Interfere with dopamine release
3) Affect how long dopamine is present in the synaptic cleft.
What are 2 ways drugs can affect production of dopamine?
1) AMPT blocks the reaction that creates dopamine
2) DOPA can increase the supply of dopamine
What are 2 ways drugs can affect release of dopamine?
1) Reserpine make vesicles leaky, causing them to escape from the vesicles
2) Some depressants convert dopamine to an ineffective form of dopamine (DOPAC)
What are 2 ways drugs can affect how long dopamine is present in the synaptic cleft?
1) Cocaine blocks reuptake
2) Typical antipsychotic drugs block dopamine receptors by binding to them (antagonist), so dopamine will have less of an effect.
What is the main brain structure involved in addiction?
Nucleus accumbens
Describe how the nucleus accumbens is involved in addiction?
Nucleus acccumbens is located in ventrial striatum of basal ganglia
Receives input from dopaminergic nucleus.
Ventral tegmental area (VTA) releases dopamine and projects to nucleus accumbens (and other parts of limbic system like amygdala, medial prefrontal cortex involved in reward processing.)
What do abused drugs tend to do with synaptic activity?
Increase the activity of dopamine and norepinephrine in the synapse.
How does nicotine affect dopamine transmission?
Increase amount of dopamine released from VTA to nucleus accumbens. So nucleus accumbens activates more strongly in response to drug consumption. (and other pleasurable experiences)
How does repeated exposure to addictive substances change your brain structure? (3)
1) increase number of receptors in nucleus accumbens
2) increase receptor sensitivity (allow drugs to bind more easily)
3) Increase in metabolism of substance in bloodstream.
What do the changes in brain structure result in?
Drug tolerance
- require a higher dose of drug to achieve same effect
Withdrawal
- refers to symptoms that occur after drug cessation
- symptoms include shaking, vomiting, hallucinations, fatigue, convulsions
What method is used to examine risk factors of a disorder in a population?
Prospective cohort study.
- See the probability of two groups (alcoholic vs non alcoholic fathers) developing alcoholism.
- Follow up for many years
- If higher probability in one group, could be genetic or upbringing factors
- If same probability, likely just environmental influences
What are the possible environmental factors identified to be involved in adddiction?
- prenatal and childhood environment
What are depressive disorders?
Refers to a group of disorders characterized by the presence of sad, empty, or irritable mood which significantly affect the individual’s function.
What are the possible genetic factors for people with early onset depression?
- more likely to have relatives with depression
Implies either genetic or early upbringing developmental effect transmitted through problems
What are the possible genetic factors involved for people with late-onset depression?
- linked to relatives with circulatory problems
possibly due to neurodegeneration of nucleus accumbens
Describe a possible genetic-environmental interaction in development of depression.
Serotonin transporter gene
Stressful life events
those with ss gene more likely to develop depression with increasing number of stressful life events.
those with ll gene less likely. regardless of no. of stressful life events, probability remains low
What do antidepressants tend to do?
tend to alter serotonin and/or norepinephrine neurotransmission.
Serotonin/Norepinephrine reuptake inhibitors
Serotnonin (only) reuptake inhibitors more popular
Why is it that the prolonged presence of serotonin/norepinephrine in the synaptic cleft is not the likely mechanism for antidepressants?
Because this logic means that serotonin levels go up within minutes or hours, and will stay increased for a long time. But antidepressants take weeks or even months to exert their therapeutic effects. Possible that there are long term changes expressed through genes but mechanism is still unclear.
Are antidepressants effective?
Depends on the severity.
Low severity – taking drug or placebo will likely see similar effects
High severity – drug is significantly more effective than placebo.
What are alternatives to antidepressants?
1) cognitive behavioural therapy (CBT)
2) exercise
3) electroconvulsive therapy
What are some treatments to depression that are under development?
1) Trancranial Magnetic Stimulation (TMS)
2) Deep Brain Stimulation (DBS)
3) Vagal nerve stimulation (VNS)
What is an evidence to show that antidepressants don’t directly improve mood?
antidepressants increase levels of neurotransmitters very fast, but improvements in mood may take weeks
Psychotherapy is preferable to drugs because: (2)
1) produces no side-effects
2) lower likelihood of relapse after the therapy
What are some characteristics of schizophrenia?
- hallucinations
- disorganised speech
- disorganised behaviour
- delusions (unjustifiable beliefs)
- weak or absent signs of emotion, speech, and socialisation
What are positive symptoms and negative symptoms?
Positive - behaviours that are present but should not be there
Negative - behaviours that are absent but should be there
What is hypothesized reason for disorganised thought?
Due to a dysfunction of working memory due to abnormal connections between cortex, thalamus, and cerebellum. Working memory and attention are core cognitive functions, when they are taxed sufficiently, can generate incoherent schizophrenic speech.
For kids with a genetic predisposition to schizophrenia, what is an important environmental factor that determines if they will actually develop schizophrenia?
Family dysfunction
At this point of research, what is the most likely mechanism of schizophrenia?
New mutations (rather than inheriting mutated genes from parents) is the most likely mechanism. Mutations are happening all the time at a slow rate. Random mutations can cause development of Scizophrenia.
How does the neurodevelopmental hypothesis explain the development of schizophrenia?
States that an important factor in the development of Schizophrenia is a disturbance in development (in-utero or early childhood).
Which factors elevate the likelihood of schizophrenia?
Poor nutrition during pregnancy Stress during pregnancy Head injury during early childhood Infections and injections during pregnancy Owning cats during childhood
What brain abnormalities do people with schizphrenia have?
Smaller left prefrontal and temporal cortices
Small cell bodies in hippocampus and prefrontal cortex. May be related to failures in connectivity
More dominant right hemisphere
What does the dopamine hypothesis state about development of schizophrenia?
States that dopamine is an important factor in schizophrenia. Dosage of medication needed to see behavioural benefits is almost perfectly correlated with the dosage necessary to block dopamine receptors. Drugs that block dopamine receptors work as an antipsychotic.
What does the Glutamate hypothesis state about the development of schizophrenina?
States that drugs that block dopamine synapses indirectly affect glutamate activity. During LTP, Schizophrenia is associated with less release of glutamate and less numbers of NMDA receptors.
How does the drug PCP (“angels dust”) induce symptoms of schizophrenia?
PCP (“angels dust”) is a drug that inhibits NMDA receptors, specific NMDA blocker. It induces many of the positive and negative symptoms of schizophrenia, without affecting dopamine.
