Psychologically, Sigmund Freud proposed that if the nursing child's appetite were thwarted during any libidinal development stage, the anxiety would persist into adulthood as a neurosis (functional mental disorder). Therefore, an infantile oral fixation (oral craving) would be manifest as an obsession with oral stimulation; yet, if weaned either too early or too late, the infant might fail to resolve the emotional conflicts of the oral, first stage of psychosexual development and they might develop a maladaptive oral fixation.
The infant who is neglected (insufficiently fed) or who is over-protected (over-fed) in the course of being nursed, might become an orally-fixated person. Said oral-stage fixation might have two effects: (I) the neglected child might become a psychologically dependent adult continually seeking the oral stimulation denied in infancy, thereby becoming a manipulative person in fulfilling their needs, rather than maturing to independence; (II) the over-protected child might resist maturation and return to dependence upon others in fulfilling their needs. Theoretically, oral-stage fixations are manifested as garrulousness (talkativeness), smoking, continual oral stimulus (eating, chewing objects), and alcoholism. Psychologically, the symptoms include a sarcastic, oral sadistic personality, nail biting, oral sexual practices (fellatio, cunnilingus, analingus, irrumatio), et cetera.
Lil self help from your friend Freud.