What is the most effective way to overcome nail biting? the urge increases when anxious and stressed out.

Many Tx options: It could be helpful to apply a non-poisonous substance on the nails that is noxious but safe such as cayenne peppers , etc. Other Tx options include bio-feedback or other psychological interventions

Multiple: People who are anxious could use multiple techniques especially cognitive behavioral therapy (CBT). You would learn to lessen your anxiety through relaxation, know how to better express your emotions, learn new coping skills and challenge any distortions in thinking. Some also use behavioral approaches like keeping busy, wearing gloves, using something bitter on nails. But my vote goes for CBT.