Diamine oxidase for use in the treatment or prevention of attention deficit hyperactivity disorder (ADHD)

1. A method of treating attention deficit hyperactivity disorder (ADHD) in a human, the method comprising:

testing diamine oxidase (DAO) activity level in plasma of the human;

responsive to results of the testing being less than or equal to a pre-defined threshold, orally administering a dosage of 0.1-50 mg of DAO to the human; and

wherein the pre-defined threshold is not greater than 80 HDU/ml.

2. The method according to claim 1 , wherein the DAO is administered in at least one of tablets, capsules, and sachets.

3. The method according to claim 1 , wherein the dosage is 2-20 mg.

4. The method according to claim 1 , further comprising administering caffeine to the human.

5. The method according to claim 4 , wherein a dosage of the administered caffeine is 1-100 mg.

6. The method according to claim 1 , wherein the administered DAO is provided with gastric protection.

7. The method according to claim 1 , wherein a form of the administered DAO is selected from the group consisting of free form, powder, lyophilised powder, microcapsules, nanocapsules, and liposomes.

8. The method according to claim 1 , wherein the DAO is included in a composition.

9. The method according to claim 5 , wherein the dosage of the administered caffeine is 5-50 mg.

10. The method according to claim 8 , wherein the composition has an enteric coating that protects the DAO from gastric acidity.