The test cohort consisted of 52 (‘group 1’) samples (from 36 patients) previously found to have antibodies to NF155 (17), NF186 (4), NF155 and NF186 (panNF, 8), CNTN1 (15) or Caspr1 (8), 51 (‘group 2’) disease controls negative for paranodal antibodies: CIDP (43), GBS (3), anti‐MAG neuropathy (3), multifocal motor neuropathy (MMN, 1), combined central and peripheral demyelination (CCPD, 1), and 57 (‘group 3’) control sera from healthy individuals (41), or patients with motor neuron disease (MND, 4), myasthenia gravis (3), genetic neuropathies (2) or non‐neurological conditions (7) (Table A1). This evidence concerns the gene CNTN1 and mild neurocognitive disorder.