Some superstitions found in witchcraft and modern black magic are interlinked with lycanthropic beliefs. 

During the Middle Age, lycanthropy was thought to be practiced by witches. The witches were believed to morph themselves into wolves that roamed throughout the European countryside frightening people, killing and devouring the travelers. Lycanthropes were even believed to be minor demons. A few werewolves whose killer instincts were exceptionally strong were thought to be the Devil himself.

Whether witches can change human beings into animals through sorcery is a question which has exercised the minds of hundreds of writers on demonology and witchcraft, amongst them, to mention a few at random, Bodin, Boguet, James I, Glanvill, Dr. Webster, Reginald Scott, his more famous namesake Sir Walter, and Charles Lamb.

Even if the werewolf was not a morphed witch, it was still related to witchcraft: tales were told about witches who arrived at Sabbaths mounting these creatures. The evil and wicked acquired, according to Paracelsus, a 16th century alchemist, the shape of a wolf upon death, or could become such creatures if they were cursed by a priest, remaining morphed for seven years. 
French writer Claude Seignolle confirms that this folklore is based upon stories of criminals cursed by priests, causing them to become werewolves. Other writers assure that the werewolf stories are originated in cases dealing with demonic possession.

To many sixteenth and seventeenth century experts, a witch could become a werewolf only by the means of dealing with the Devil. These “witches” were usually believed to have no other supernatural ability. Many contemporary werewolf legends are originated in that obscure era. All these popular beliefs are so rooted into our culture that it is difficult to tell where the boundary between myth and reality is.

Some lycanthropes (according to tales from the 17th century) assured people that they really were wolves and that their fur grew inside their body.

If we remember the drugs used by witches as “metamorphosing ointments” and self-suggestion, it is very possible that this induced, in the ones who took them, hallucinations of being werewolves, without really being affected by lycanthropy, only by the effects of such drugs combined with suggestion, but this doesn’t explain others seeing them as werewolves.