Addictive, yes they are. To varying degrees. Drug safety and addiction risk aren't synonymous, though. Let me give you a specific example that illustrates the difference.
30 years ago when I needed a powerful painkiller I would be prescribed codeine. This is an addictive opioid with a potential for overdose. If used correctly, neither of those things will necessarily happen. Since I am not allergic to opiates, when used correctly this is a safe drug. It can perform the function - alleviating severe pain - without negative consequences.
Today I can only get Vicodin. Vicodin is synthetic codeine spiked with acetaminophen. The purpose of the acetaminophen is to destroy my liver if I take "too much". Instead of becoming addicted or passing out from overdose, I will suffer liver failure and death. At this time 50% of the liver failure fatalities in the United States result from acetaminophen abuse.
Although no chemical substance is truly "safe" - you can overdose on water, after all - Vicodin is less safe than codeine, because equivalently pain-relieving doses of Vicodin are more likely to result in death or permanent liver compromise. Today physicians are encouraged to prescribe Vicodin, and strongly discouraged from prescribing codeine. In fact the DEA will be all over them if they routinely prescribe codeine, and you'll see them in the headlines as "Dr. Feelgood pushing dope to junkies" before long.