"Additionally, we considered it especially serious that the man threatened to sell the girl," the Gothenburg District court wrote in a statement, according to the TT news agency.
"The court has also taken into consideration that the man has a mental disorder, and was therefore unable to control his actions."
The kidnapping took place in Gothenburg in November, when the man snatched the girl as she made her way to school. He kept her hostage for 18 hours.
Hundreds of volunteers took to the streets to look for the nine-year-old, a search party which the 25-year-old man also joined. It was he himself who eventually turned up with the girl, claiming that he found her in a nearby park.
The man had taken her to his apartment, where he put his fingers in her mouth and threatened to sell her as a sex slave.
The girl appears not to have been a victim of any sexual attacks, nor did she appear in any material in the man's porn collection.
The man tied her up on two occasion and warned her that his parents were dangerous.
The court judged, however, that his threats were empty. The man talked with the girl about how she could get back home without revealing the his identity.
The court ruled that the man had neither motive nor desire to hurt the girl, and that he was simply acting on impulse.
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The 25-year-old was also sentenced for assault and child pornography crimes, and was also ordered to pay 120,000 kronor ($18,840) in damages to the girl.