They compared the genetic makeup of 132 healthy internet users with those of the same number of likely Internet addicts - defined as someone who obsessively thought about the Internet and whose sense of wellbeing was shaken if they couldn't go online.
Their findings, published in the September issue of Journal of Addiction Medicine, showed problematic users more often carried a variation of the CHRNA4 gene, which is typically linked to nicotine addiction.
"What we already know about the nicotinic acetylcholine receptor in the brain is that a mutation on the related gene promotes addictive behaviour," said the study's lead author, Christian Montag from the Department for Differential and Biological Psychology at the University of Bonn.
Nicotine from tobacco fits - just like acetylcholine, which is produced by the body - like a key into this receptor. Both these neurotransmitters play a significant role in activating the brain's reward system.
Internet addiction is not just a figment of our imagination, said Montag.
"It seems that this connection is not only essential for nicotine addiction, but also for Internet addiction," he said.
Montag told The Local the variation was more common in women, a finding he wants to investigate further because numerous surveys have indicated that men are more prone to Internet addiction than women.
The psychologist said that the sex-specific genetic finding may result "from a specific subgroup of Internet dependency, such as the use of social networks or such."
He added that studies including more subjects were required to further examine the connection between this mutation and Internet addiction.
"But the current data already shows that there are clear indications for genetic causes of Internet addiction."
And he suggested, “If such connections are better understood, this will also result in important indications for better therapies.”