Methods for diagnosing an attention-deficit/Hyperactivity disorder

A method for diagnosing attention-deficit/hyperactivity disorder (ADHD) in a human patient, comprising:

• (a) obtaining a ratio of
• (i) the mean membrane potential of cells of a test human patient incubated in vitro in the presence of a compound that alters Na+K+ ATPase activity, but in the absence of K+, to
• (ii) the mean membrane potential of cells of the test human patient incubated in vitro in the absence of the compound that alters Na+K+ ATPase activity, but in the presence of K+;
• and
• at least one of the following steps (b) or (b′):
• (b) comparing the ratio obtained in (a) to a control ratio, wherein the control ratio is the ratio of
• (iii) the mean membrane potential of corresponding control cells of one or more humans known to not have ADHD incubated in vitro in the presence of a compound that alters Na+K+ ATPase activity, but in the absence of K+, to
• (iv) the mean membrane potential of corresponding control cells of one or more humans known to not have ADHD incubated in vitro in the absence of the compound that alters Na+K+ ATPase activity, but in the presence of K+,
• wherein when the ratio obtained in (a) is significantly higher than the control ratio obtained in (b), said test human patient is diagnosed as having ADHD;
• (b′) comparing the ratio obtained in (a) to a ADHD control ratio, wherein the ADHD control ratio is the ratio of
• (v) the mean membrane potential of corresponding ADHD control cells of one or more humans known to have ADHD incubated in vitro in the presence of a compound that alters Na+K+ ATPase activity, but in the absence of K+, to
• (vi) the mean membrane potential of corresponding ADHD control cells of one or more humans known to have ADHD incubated in vitro in the absence of the compound that alters Na+K+ ATPase activity, but in the presence of K+,
• wherein when the ratio obtained in (a) is not significantly different than the ADHD control ratio obtained in (b′), said test human patient is diagnosed as having ADHD,
• wherein each mean membrane potential is determined by incubating the cells in vitro in buffer comprising a potential-sensitive dye, resuspending the cells in potential-sensitive dye free-buffer, and measuring cell fluorescence.