What are the effects of marijuana and Adderall (amphetamine/dextroamphetamine) on executive function and learning?

Effects of Marijuana and Adderall on Executive Function and Learning

Cannabis use during adolescence negatively impacts executive function and learning by altering brain structure and function, while Adderall can improve attention and focus but may have reduced effectiveness when combined with cannabis. 1, 2

Cannabis Effects on Executive Function and Learning

Cannabis use has significant impacts on cognitive function, particularly during adolescence when the brain is still developing:

• Structural and Functional Brain Changes:

  • Altered gray matter volume and cortical thickness 1
  • Disrupted prefrontal cortex connectivity 1
  • Inhibited GABAergic inhibitory action on glutaminergic neurons, increasing susceptibility to excitotoxicity 1

• Cognitive Impairments:

  • Deficits in episodic memory, decision making, attention, and processing speed 1
  • Acute impairment of memory and learning in adults 1
  • Potential negative effects on brain development in adolescents 1
  • Possible reduction in motivation 1

• Timing of Use Matters:

  • Early initiation of cannabis (particularly before age 13) is associated with greater neural changes and higher risk of continued use 1
  • Neural changes occur more rapidly in adolescents than adults 1
  • Many cannabis-related structural changes are unique to adolescents 1

Adderall Effects on Executive Function and Learning

Adderall (amphetamine-dextroamphetamine) is primarily used to treat ADHD and narcolepsy:

• Therapeutic Effects:

  • Improves attention, focus, and academic productivity 3
  • Reduces reaction time variability on continuous performance tests 4
  • Decreases reaction times on working memory tasks 4

• Mechanism of Action:

  • Stimulates the release of norepinephrine affecting both α- and β-adrenergic receptor sites 5
  • Affects dopaminergic signaling pathways 2

Combined Effects of Marijuana and Adderall

The interaction between cannabis and Adderall presents concerning patterns:

• Reduced Adderall Effectiveness:

  • Chronic exposure to inhaled cannabis high in THC suppresses Adderall-induced brain activity 2
  • Blunted response to Adderall characterized by decreased positive BOLD signal and increased negative BOLD signal 2
  • Brain regions most affected include prefrontal cortex, nucleus accumbens, ventral pallidum, caudate/putamen, and thalamus—areas critical for executive function 2

• Additive Cardiovascular Effects:

  • Combined use produces additive effects on heart rate 4
  • Potential for increased cardiovascular risk 6

• Variable Cognitive Effects:

  • THC can mitigate some of the reaction time improvements provided by Adderall 4
  • THC increases commission errors on continuous performance tests 4

Clinical Implications

• Recovery Potential:

  • After a 2-week washout period from cannabis, the blunted response to Adderall may normalize 2

• Increased Risk for Vulnerable Populations:

  • Adolescents are particularly vulnerable due to ongoing neurodevelopment 1
  • The developing adolescent brain shows unique neurochemical responses to substances 1

• Screening Recommendations:

  • Consider screening for cannabis use patterns in patients prescribed Adderall 6
  • Use validated screening tools like CRAFFT 2.1+N or BSTAD to assess substance use 1

Pitfalls and Caveats

• Cannabis potency has increased significantly over time (from 9% THC in 2008 to 17% in 2017), with concentrates reaching up to 70% THC 6
• Higher THC concentrations are associated with greater risk of adverse effects 6
• Different methods of cannabis consumption (smoking, vaping, edibles) may present different risk profiles 6
• Concurrent use may lead to escalation of psychostimulant use to overcome the blunted effects 2

The evidence strongly suggests that cannabis use, particularly during adolescence, negatively impacts executive function and learning through multiple mechanisms. While Adderall can improve attention and cognitive performance in appropriate clinical contexts, concurrent cannabis use may significantly reduce its effectiveness and potentially lead to increased dosing to achieve the desired effects.