Wrinkles occur as part of the natural aging process, when the collagen and elastin in the connective tissue of the skin become weak and break down due to changes in fibroblasts that produce collagen and elastin.
Premature or excess wrinkles can also be caused by factors like too much exposure to sunlight or harsh environments, smoking, use of certain drugs, excessive stress, sudden weight loss, loss of vitamin E, and genetic predisposition.