Dependence & tolerance
- Addiction is the physical and/or psychological dependence on the use of drugs or other substances e.g. alcohol, or dependence on activities or behaviours e.g. gambling, shopping
- Examples of addiction include but are not limited to, smoking, opiate addiction, alcohol addiction and gambling addiction
- Physical dependence is the physiological state of adaptation to a substance resulting in tolerance , the absence of which produces withdrawal
- Psychological dependence is the compulsion to use a substance for its pleasurable effect which can also lead to anxiety, memory issues, mood swings and an obsession with the substance
- Physical and psychological dependence overlap, with key behaviours being over-use, taking the substance even when you know it is bad for you, problems maintaining everyday activities and inability to stop
- Tolerance can be explained by the idea of homeostasis - the brain tries to maintain its ‘balance’ but if large amounts of an addictive substance are consumed regularly, then it disrupts this balance and eventually the brain readjusts by rebalancing at the new level
- There are two types of tolerance:
- Metabolic tolerance is when the substance is metabolised quicker and therefore leaves the body quicker
- Cellular tolerance is when there are changes in the responsiveness of the neurons as the brain tries to rebalance at a new level
- Both types of tolerance result in more and more of the substance being needed to produce the same level of effect
Tolerance results in more substance needed to achieve the same effect.