Is it safe to use marijuana while on enbrel (etanercept)?

Not generally. This applies to all questions regarding safety of drug use: not safe! to adequately answer your question of safety, someone needs to put together a study of people smoking weed while on Enbrel (etanercept) and see if any of them would have problems. Due to all kinds of ethical and legal cncerns, that study is unlikely to happen. To be safe, don't do drugs and get help!
Is marijuana safe? . The first question should be "is it safe to use marijuana'? Assuming the person giving you an answer is not actually using it then you might be able to get sound advice. Most neuro scientists would point out the many harmful effects that may cause permanent damage. There are much safer medications to use for anxiety and stress.