People develop drug addiction because drugs stimulate the release of endorphins. A sudden lack of the stimulation negatively affects the mental health of those starting recovery, increasing a risk of relapse. Pet therapy, also called animal-assisted therapy, can encourage the release of endorphins. This makes a switch to a life free of drugs more comfortable for the patient.
Pet therapy can be very beneficial, as you can see in the infographic. But AddictionResource authors explain that it works well in conjunction with other treatment methods. For example, the presence of animals can help patients be more open an honest during psychoeducational therapy.