While pycnogenol might impact cognition or ADHD, the existing evidence is not sufficient to draw any meaningful conclusions.
Both pycnogenol and oligopin (a different standardized extract of French maritime pine bark) have demonstrated mixed and unconvincing results when used in ADHD. Some research has reported reductions in the symptoms of ADHD (e.g., inattentiveness, hyperactivity) in children, but the effects tend to vary based on who is assessing the symptoms and what measurement tool is used.[1][2][3] Pycnogenol does seem to improve antioxidant status in children with ADHD, but whether this is clinically meaningful still needs to be determined.[4][5]
Several trials have assessed the effects of pycnogenol on cognition in a variety of populations, including university students,[6] people with mild cognitive impairment,[7] professionals without apparent health conditions,[8] people with elevated levels of oxidative stress,[9] and elderly individuals.[10] All studies reported improvements in some aspect of cognition (e.g., alertness, memory, attention), but only one study was placebo-controlled, which undermines the validity of these results.