Heroin is way way stronger than codiene,so the withdrawls may be similar (flu like symptoms,insomnia,rls,anxiety) but the heroin
w/d will be way worse,with even longer mental withdrawls. Codiene
w/d will be quite uncomfortable as well. It's a drug that also alters your brain,so if you've been on it for months it could take a few weeks to start feeling a clear head. If you've been on it for years then it could take up to months for your brain to heal.