A Canadian study found that heavy marijuana use is associated with decreased IQ scores, but light and former use are linked to modest gains. The research, which followed 70 subjects over several years, suggests that the effects of marijuana on intelligence may be more complex than previously thought.
Research found that older girls with ADHD often internalize their feelings and exhibit social problems, anxiety, and depression. Higher verbal IQ scores were unexpectedly associated with ADHD symptoms in girls, differing from previous research on boys.
Pediatric researcher Holly A. Ruff warns against applying large-group study findings to explain individual behavior, citing limitations in IQ testing and the complexity of vulnerability/resilience. Vulnerable children from disadvantaged backgrounds may face additional risk factors such as poor nutrition and lack of protective factors.
A study by Brown University researchers found that prenatal cocaine exposure can lead to lower IQ scores and language performance in children. The analysis of over 800 school-age children revealed a significant impact on intelligence, with an average IQ score reduction of 3.26 points.
Researchers are using outdated techniques, missing significant discoveries. Expert recommends revisiting studies and applying modern computational methods to correct issues.