Substance misuse

• Substance misuse disorder is the consumption of substances that leads to the involvement of social, psychological, physical, or legal problems.
• Demographics:

  • Cannabis is most common substance in 16-59 year olds - followed by cocaine and ecstasy
  • Alcohol misuse is the fifth biggest risk factor for death across all ages
• Substance dependence requires at least two of the following:

  1. Impaired control over substance use
  2. Increasing priority over other aspects of life or responsibility
  3. Psychological features suggestive of tolerance and withdrawal
• Subtypes of substance misuse disorder:

  • Low risk use
  • Hazardous substance use
  • Harmful substance use
  • Substance dependence
• Pathophysiology:

  • affects neurotransmitters such as the balance between glutamate, GABA and dopamine
  • Consuming the substance causes release of dopamine which gives off pleasurable feelings - operant conditioning
  • alcohol and opioids interact with the inhibitory neurotransmitter GABA- leads to more sedative hormones (GABA)
  • exposed chronically results in neuroadaptation - upregulates glutamate - withdrawal symptoms occur when there is a sudden drop in GABA, resulting in disrupted homeostasis and too much glutamate
• Tolerance refers to a loss of effect when taking the same dose. The person may keep increasing the dose to achieve the desired effects. Tolerance occurs with most psychoactive substances over time.
• Psychological addiction:

  • Brains reward pathway = mesolimbic pathway - primary neurotransmitter is dopamine
  • Structures = ventral tegmental area, nucleus accumbens, amygdala and prefrontal cortex
  • Addictive substances release dopamine within the mesolimbic pathway - pleasure
  • Repeated exposure reduces the number and sensitivity of the dopamine receptors - tolerance
  • Cues for the substance or behaviour are embedded into the amygdala
• Opioids:

  • Heroin
  • Morphine
  • Oxycodone
  • Codeine
  • Stimulate opioid receptors
• Stimulants:

  • Cocaine - blocks reuptake of dopamine by presynaptic membrane
  • MDMA (ecstasy) - stimulated the release of serotonin and blocks its reuptake
  • Methamphetamine - stimulates the release of dopamine and blocks reuptake
• Depressants:

  • Alcohol
  • Benzodiazepines
  • Stimulates GABA receptors
• Hallucinogens:

  • LSD
  • Psilocybin
  • Stimulate serotonin receptors, particularly 5-HT2A receptors
• Cannabinoids:

  • Cannabis
  • Stimulates cannabinoid receptors
  • CB1 and CB2 receptors
• Anticonvulsants:

  • Pregabalin - GABA analogue
  • Gabapentin - Blocks voltage-gated calcium channels in the presynaptic membrane, reducing the release of excitatory neurotransmitters
  • Lamotrigine and sodium valproate - block voltage gated sodium channels to reduce neurotransmission
• Nicotine:

  • Cigarettes and vapes
  • Stimulates nicotinic acetylcholine receptors
• Substance misuse disorder:

  • Consumption of substances that leads to the involvement of social, psychological, physical, or legal problems
  • Among people aged 16-59, the most common substance is cannabis - followed by cocaine and ecstasy
  • Alcohol misuse is the 5th biggest risk factor for death across all ages
• Subtypes of substance misuse disorder:

  1. Low risk use
  2. Hazardous substance use
  3. Single episode of harmful substance use
  4. Harmful pattern of substance use
  5. Substance dependence