cognitive and intellectual functioning in addiction Flashcards
Introduction- cognitive and intellectual functioning in addiction
PFC controls executive functions such as memory, response inhibition and decision making. PFC part of the trajectory of the mesocorticolimbic dopamine pathway, which is also comprised of the VTA and NAcc and is implicated in most forms of addiction. Altered neurochemical functioning assoicated with drug use could therefore lead to long lasting changes in the pfc. Thus cognitive and intellectual deficts may be a symptom of drug abuse which subsequently contributes to its development and maintenance. We know that people who have suffered from drug addictions are impaired on a range of exec funct tasks related to the PFC, such as weakened response inhibition , Increased risk-taking, Poor decision-making, Abnormal delay discounting. This essay will present evidence for cognitive and intellectual impairment associated with drug abuse and discuss the neurobiological basis for this association.
What is delayed discounting
Impulse control can be measured using ‘delayed discounting tasks.’ This involve asking participants to make choices about whether to obtain a small instant reward or a larger reward some time in the future. For example, a hypothetical $1,000 reward may be delayed at intervals ranging from 6 hr to 25 years, and immediate rewards varies from $1 to $999. The participant is asked to choose a reward.
2 studies for delayed discounting in drug addiction
MacKillop et al 2011. Conducted a meta-analysis investigating delayed discounting in a variety of addictions including cigarettes, cocaine, amphetamine, heroin, marijuana and gambling. Results showed that in the clinically addicted samples, deficits in delayed discounting were strongly associated with degree of addiction (i.e. self-reported dependency). These data provide further evidence that rapid discounting of delayed rewards may be a feature central to impulse control and addictive disorders.
Hanson et al 2011In the present study, we examined patterns of neuropsychological function over these 10 years in relation to the AOD (alcohol of drug?) trajectories identified for youth as they transition into their twenties. Participants were part of a longitudinal research project following adolescents with and without A/SUD who received neuropsychological examinations at baseline and up to 7 times thereafter spanning 10 years (N = 213; 46% female at baseline). Neuropsychological trajectories were significantly related to substance involvement patterns over time on measures of verbal learning and memory (ps = .011 to
What are the 8 constructs measured by JEF
Planning (PL), Prioritisation (PR), Selective Thinking (SE), Creative Thinking (CT) and Adaptive Thinking (AT). Prospective memory: Action-Based Prospective Memory (ABPM), Event-Based Prospective Memory (EBPM) and Time-Based Prospective Memory (TBPM)
Briefly describe the JEF
- An ecologically valid task that assesses multiple aspects of executive functions.
- Virtual reality games where individuals are in an office building and are given a ‘to do’ list by the manager.
- Each task was created to make sense within an office environment and address various aspects of exec function simultaneously.
- Briefly, the task involved the participant being invited to play the role of an office-temp worker whose main goal was to organise a meeting later that day and to prepare an appropriate room for this meeting. They were informed that the manager had left a list of tasks for them to complete and that all information could be found in their office. The responsibility of planning for overall task completion was given to the participant with no clues as to possible solutions or courses of action.
Study showing the effects of alcohol on executive functioning
Jansari and Chipman- Used JEF to look at recovered alcoholics (abstinent for ~ a decade) wanting to see whether there were any long-lasting detrimental effects on exec functions after past alcohol abuse. Wanted to investigate whether if a person is impaired in their exec functions during the period of addiction, and neuro-adaptational changes go back to their normal level due to abstinence, would the system have reverted back to normal and would have exec functions been restored? Found a significant difference between recovered alcoholics and normal controls on all types of exec f (apart from planning where the difference was quite small), suggesting that there are very long term exec f deficit acquired from chronic substance use.
D’Souza study showing the effects of cannabis on executive functioning
• D’Souza et al 2004: On three test days at least a week apart, the researchers administered THC to 22 test subjects—including Yale medical students and undergraduates and other volunteers. All had used cannabis previously but none had ever been diagnosed with cannabis abuse disorder or a major psychiatric disorder. On each test day the subjects received one of three injections, a placebo or a low or medium dose of THC, before taking a series of behavioral and cognitive tests. The subjects reported how they felt, using a scale of feeling states associated with cannabis effects—high, calm, relaxed, tired, anxious and panicked. THC induced temporary responses similar to the three domains of schizophrenia: positive symptoms such as paranoia and disorganization of thinking, negative symptoms such as blunted affect and reduced spontaneity, and cognitive deficits such as memory lapses.
Jansari et al study showing the effects of cannabis on executive functioning
Jansari et al found a significant difference in accuracy on cognitive constructs measuring exec functions between users and non-users of cannabis. The most significant difference was in memory tasks, especially action based prospective memory (ABPT) and time based prospective memory (TBPM).
Study showing the effects of cocaine on executive functioning
- Iowa gambling task On each trial, participants must select a card from one of four decks on a computer screen. Each deck is associated with specific reward and punishment contingencies, to which the participant is unaware of. Two decks are associated with large gains outweighed by intermittent larger losses, while the other two decks are associated with smaller gains which outweigh intermittent smaller losses. People without exec function problems tend to gravitate towards certain decks after working out which decks are more beneficial.
- Verdejo-Garcia et al 2007 Investigated relationship between cocaine and weed users and IGT learning. Found that both cocaine and weed users performed worse than controls. Cocaine users showed the smallest increase in performance ○ All groups shows learning between session 1 and 2 however. Further, dose related measures of cocaine and weed use predicted IGT performance where the heavier the drug use, the lower the performance.
Study showing the effects of cannabis use on intellectual functioning
• The Dunedin New Zealand longitudinal study.
Focused on 1037 people born between 1972-1973 in Dunedin, New Zealand Pps were assessed every two years in childhood and adolescence.
• Meier et al 2012 Used Dunedin sample to conduct a prospective, longitudinal examination of the degree to which persistent cannabis use is associated with changes in long-term neuropsychological functioning. Used IQ scores taken across late childhood/early adolescence (i.e. pre-cannabis use) and compared with IQ at age 38, as well as with other neuropsychological tests taken at this age. Previous year cannabis use/dependence recorded from age 18 through 38. There was a drop in IQ by about 6 points for heavy users – heavy regular use associated with an effect size of -0.38/-0.35 (in stats, this is a medium effect size). There were no major differences across IQ sub-tests (though spatial reasoning tests showed smaller decline,) implying it’s a general neuropsychological problem rather than a specific one. However, it was found that processing speed and executive function tests showed strongest decline. Decline in IQ remained significant when controlling for other licit and illicit substance use, diagnosis of schizophrenia, and years of education. Adolescent onset users showed greater decline than adult onset users The decline for those who began using in adolescence was much higher than those who started use in adulthood. Shows than WHEN you start using has an impact not just using on its own perhaps as exec functions are still forming. Heaviest adolescent onset users show decline of -0.55 (~8 IQ points). Adult onset heavy users showed a negligible decline in IQ. Study showed that IQ decline was apparent whether cannabis was used infrequently or frequently in teens. Shows that cessation of use didn’t fully restore neuropsychological functioning among teen onset former persistent cannabis users. Suggests some level of persistence for neurotoxic effects caused by heavy adolescent usage.
Limitations of Meier et al 2012
• Limitations- One issue complicating all of this, particularly in longitudinal studies, is the composition of cannabis itself, evolutionary speaking over time evidence has shown that the THC (the key psychoactive ingredient) has increased over time. The THC content around the world was relatively stable then increased significantly from 2000 (from around 5% to 10% in 2008; National Institute of drug abuse, 2008). means that when comparing longitudinal data, it is likely that the cannabis compared is significantly different (apples and oranges). Therefore, the longitudinal study loses validity. However, increases in THC content of cannabis smoked over long time periods is unlikely to confound results beyond useful interpretability. In other words, whilst the assumption that THC consumption remained stable over the time period of interest is likely not met, these studies still provide valuable insight into long term use.
