The present invention (patent filed) provides strategies for diagnosing and for predicting / monitoring treatment efficacy, in the case of attention deficit hyperactivity (ADHD) in human subjects. By simple biochemical method (Enzyme Linked Immuno Sorbent Assay, ELISA), the present invention is evaluating the level of serum auto antibodies (aAbs) to human dopamine transporter (hDAT). This method is based on specific peptide fragments (patented) to be used as antigen sequences in order to detect hDAT aAbs in the blood and in other biologic fluids. The inventors have discovered that present invention can predict and/or monitor the efficacy of “Ritalin-like” psycho-stimulant drugs: therapeutic strategies, when combined with the present "prognostic" invention, can be practiced more effectively. In particular, biomarkers of present invention can be used to - verify and/or confirm ADHD diagnosis, - select drug therapies and avoid prescription of wrong medication (for example, “Ritalin-like” psycho-stimulant drugs for patients without verified ADHD diagnosis), - predict and/or monitor the effectiveness and progress of therapies for ADHD. Key application(s)- It is an object of present invention to provide methods and biochemical markers for distinguishing between neuropsychiatric symptoms, which might be very similar to ADHD in: alcoholism, drug abuse, conduct disorder, antisocial personality, addictive/compulsive behavior.