1) Anxiety disorder 
Arithmomania is a mental disorder that may be seen as an expression of obsessive–compulsive disorder (OCD). Individuals suffering from this disorder have a strong need to count their actions or objects in their surroundings. Sufferers may for instance feel compelled to count the steps while ascending or descending a flight of stairs or to count ...
numbers & counting [synonym - arithomania] => [arithmo-] (Greek) meaning 'number'
obsessive preoccupation with numbers
<psychiatry> A morbid impulse to count. ... Origin: G. Arithmeo, to count, fr. Arithmos, number, + mania, madness ... (05 Mar 2000) ... 
Type: Term Pronunciation: ă-rith′mō-mā′nē-ă Definitions: 1. A morbid impulse to count.
arithmomania A compulsive desire to count objects and to make calculations; such as, counting paces when walking, steps in a staircase, etc. A common symptom in obsessive-compulsive disorder.