Developed by Chuan-Yun Li, Xizeng Mao and Liping Wei of the Centre for Bioinformatics at Peking University, the KARG - or Knowledgebase for Addiction Related Genes - database is the first for addiction-related genes and features extensive annotation.

The designers amassed over 2000 items of evidence from the literature that linked genes and chromosome regions to addiction.

They identified 1500 human genes and then performed a meta-analysis of 396 of them. This allowed them to identify 18 molecular pathways that were statistically significant.

"In particular, five of them were common for four types of addictive drugs [cocaine, opiates, alcohol and nicotine], which may underlie shared rewarding and addictive actions," the authors wrote in an open access paper, Genes and (Common) Pathways Underlying Drug Addiction, in PLos Computational Biology.

Those common pathways identified are neuroactive ligand-receptor interaction, long-term potentiation, the MAPK signalling pathway and two pathways not previously linked directly to addiction: the GnRH signalling pathway and gap junctions, groups of electrical synapses that are also an important type of connection for neuroglial cells.

The authors suggest these pathways could serve as interesting hypotheses for further experiments.