Claim: Sexual addiction is falsely believed to be when ΔJunD (intronless gene is a member of the JUN family) opposed ΔFosB, which regulates behavior towards natural rewards like drugs.
Evidence: ΔJunD is the transcription factor which directly opposes ΔFosB. ΔFosB also plays an important role in regulating behavioral responses to natural rewards, such as palatable food, sex, and exercise. Sexual activity is an intrinsic reward that has been shown to act as a positive reinforcer, strongly activate the reward system, and induce the accumulation of ΔFosB in part of the striatum (specifically, the nucleus accumbens). Thus, ΔFosB is also the key transcription factor involved in addictions to natural rewards as well, and sexual addictions in particular, since ΔFosB in the nucleus accumbens is critical for the reinforcing effects of sexual reward. The protein encoded by this intronless gene is a member of the JUN family, and a functional component of the AP1 transcription factor complex.