Nucleic acid molecules encoding an ATP-gated ion channel P2X7R which contains a mutation or a deletion are disclosed. Polypeptides encoded by the nucleic acid molecules and antibodies that specifically are directed to these polypeptides are disclosed. Aptamers that specifically bind the nucleic acid molecules, and primers for selectively amplifying the nucleic acid molecules are provided, kits, compositions, particularly pharmaceutical and diagnostic compositions comprising the nucleic acid molecules, vectors, polypeptides, aptamers, antibodies and/or primers, are provided. Methods for diagnosing affective disorders associated with a non-functional P2X7R protein, an altered ATP-gating of the P2X7R protein, an over- or underexpression of the P2X7R protein or associated with the presence of any one of the nucleic acid molecules or polypeptides encoded thereby are disclosed. Additionally, the present invention relates to uses and methods for treating affective disorders employing a functional or non-functional ATP-gated ion-channel P2X7R, such as treatment with modulators of P2X7R activity.