Table 2.

Overview of neurotransmitter system involvement in six types of behavioral addiction and similarities to and differences from key results in substance use disorders

Behavioral addiction	Key results	Similarities to/differences with key results in substance use disorders
gambling	Dopamine: Dopamine implicated but precise nature unclear; limited findings negative comparing PG with controls in D2-like receptor availability; individual differences in dopamine release and function; some results suggest differential response to agonist and antagonist administration in PG; clinical trial results with antagonists have been negative	Data suggest reduced numbers of D2-like receptors in SUDs compared to controls; substance use has been related to release in some studies but also individual differences; some clinical trial findings with antagonists positive, while others negative, with limited clinical utility demonstrated
	Serotonin: Varied neurochemical findings suggest differential function in PG compared to controls; negative and mixed clinical trial findings with reuptake inhibitors and a receptor antagonist suggest possible individual differences in function	Neurochemical studies suggest differential function; some clinical trial results with reuptake inhibitors have been positive while others negative, suggesting possible individual differences in activity
	Opioids: Multiple positive clinical findings suggest role for opioidergic systems in PG	Multiple positive clinical findings suggest role for opioidergic systems, particularly for opiates and alcohol
	Glutamate: Preliminary positive clinical findings suggest it may have a role, particularly in impulsive and compulsive behaviors	Preliminary positive clinical findings suggest it may have a role, particularly in impulsive and compulsive behaviors
	Norepinephrine: Elevated at resting state and found to increase during gambling; blunted growth hormone response to clonidine	Elevated during use of some substances, particularly cocaine
Internet use	Dopamine: Low levels of dopamine transporter expression in striatum	Low levels of dopamine transporter expression in striatum in some studies though higher levels in other studies
Video-game playing	Dopamine: The role of dopaminergic activity has not been investigated directly; limited and preliminary findings related to genotypes associated with possible alterations in dopamine signaling suggest possible differences from controls in dopaminergic activity.	Evidence suggests differences in dopaminergic activity between substance dependent individuals and controls
shopping	Serotonin: Positive results in an open-label clinical trial but negative results in controlled trials with serotonin reuptake inhibitors	Clinical results with reuptake inhibitors have been positive in some studies and negative in others.
kleptomania	Serotonin: Some neurochemical results suggesting involvement but negative clinical results	Neurochemical studies differences from controls in serotonergic function; clinical results inconclusive and suggest possible individual differences
	Opioids: Positive preliminary clinical results suggest a possible role for opioidergic system involvement	Positive clinical results suggest a role for opioidergic systems in SUDs
sex	Serotonin: Limited positive clinical results suggest possible role for serotonergic activity	Clinical results with reuptake inhibitors have been positive in some studies and negative in others.