I have a 10 year old male with both significant adhd and ocd, as well as mild-moderate anxiety. i want to give mono-therapy. suggestions? (effexor?).

Depends on primary: It depends on whether or not one issue is primary or secondary to another, or whether this is a true comorbidity. With ocd stimulants can worsen anxiety and cause tics. Strattera should be considered with an ssri like zoloft for the ocd. I have not found Effexor (venlafaxine) to be very helpful for either condition, but there are scattered case reports to support its use in one or the other conditions, not both.

ADHD +Anxiety: Medications that are likely to help this combination of symptoms are tricyclic antidepressants such as Imipramine or desipramine. Other antidepressants/anti anxiety meds are not usually effective for symptoms of adhd unless the inattentiveness is due to a very high anxiety level.