From the Guidelines
Decreased processing speed in a 20-year-old patient can result from multiple causes, including substance use, such as cannabis, which has been shown to contribute to deficits in episodic memory, decision making, attention, and processing speed, as highlighted in a recent study published in The Lancet Child and Adolescent Health 1.
Potential Causes of Decreased Processing Speed
Some potential causes of decreased processing speed in a 20-year-old patient include:
- Neurological factors, such as traumatic brain injury, neurodevelopmental disorders like ADHD, learning disabilities, or early-onset neurodegenerative conditions
- Psychological factors, such as depression, anxiety, PTSD, or chronic stress, which can significantly impair cognitive processing
- Medical conditions, like hypothyroidism, vitamin deficiencies (particularly B12, folate, or vitamin D), anemia, sleep disorders, or undiagnosed seizures
- Substance use, including alcohol, cannabis, or prescription medications with cognitive side effects
- Lifestyle factors, like chronic sleep deprivation, poor nutrition, or extreme fatigue, which can impact cognitive function
Importance of Comprehensive Evaluation
A comprehensive evaluation, including neuropsychological testing, medical examination, blood work, and possibly neuroimaging, is necessary to determine the specific cause of decreased processing speed in a young adult, as early intervention can often improve outcomes and prevent further cognitive decline, as noted in a study on minimal hepatic encephalopathy 1.
Recent Findings on Substance Use
Recent findings suggest that cannabis use during adolescence can lead to long-term changes in brain structure and function, including alterations in the prefrontal cortex, which can affect processing speed and other cognitive functions 1.
Clinical Practice Recommendations
Clinical practice recommendations emphasize the importance of assessing cognitive and adaptive strengths and weaknesses, especially at transition to adulthood, and providing evidence-based supports and services to individuals with decreased processing speed, as outlined in a study on 22q11.2 deletion syndrome 1.
From the Research
Potential Causes of Decreased Processing Speed
The potential causes of decreased processing speed in a 20-year-old patient can be attributed to various factors, including:
- Neuropsychiatric conditions, such as attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, and psychotic disorders 2
- Cognitive ability, with higher cognitive ability potentially being protective against the impact of slow processing speed on adaptive outcomes 3
- Neurobiological predictors, such as declines in frontal and cerebellar gray matter, which can affect processing speed 4
- Psychopathology symptom dimensions, including inattention, which can associate with slow processing speed 2
Neurobiological Predictors
Neurobiological predictors, such as age-related changes in brain structure and function, can contribute to decreased processing speed 4. Additionally, certain medications, such as methylphenidate and atomoxetine, can modulate functional connectivity during working memory tasks and improve processing speed in individuals with ADHD 5.
Psychopathology and Processing Speed
Psychopathology, including psychosis, can impair processing speed, and this impairment can be distinct from the effects of normal aging 6. The relationship between psychopathology and processing speed is complex, and further research is needed to understand the underlying mechanisms 2.
Cognitive Functions and Academic Achievement
Processing speed can have direct and indirect effects on academic achievement, with indirect effects mediated by working memory 2. Understanding the relationship between processing speed, cognitive functions, and academic achievement can inform the development of interventions to support individuals with decreased processing speed 3, 2.