What is the primary action of psychostimulants in treating ADHD?

Psychostimulants primarily function by increasing the levels of dopamine and norepinephrine in the brain. This is significant in the treatment of Attention-Deficit Hyperactivity Disorder (ADHD), as both of these neurotransmitters play crucial roles in regulating attention, impulse control, and overall behavioral response.

The increase in dopamine levels helps to enhance motivation and focus, which are often impaired in individuals with ADHD. Similarly, the elevation of norepinephrine levels contributes to improved attention and executive function. By enhancing the availability of these neurotransmitters, psychostimulants help mitigate the symptoms associated with ADHD.

Other options reflect mechanisms that do not align with the primary action of psychostimulants. For instance, decreasing dopamine levels or inhibiting norepinephrine release would generally have the opposite effect needed to manage ADHD symptoms. Enhancing serotonin activity, while it could have therapeutic benefits in other mood-related disorders, does not target the specific pathways relevant to ADHD management as effectively as increasing dopamine and norepinephrine does. Hence, the focus on boosting these particular neurotransmitters is what makes option C the correct answer.