The final years of Deakin's political career coincided with the early stages of a degenerative neurological condition, with memory loss as the primary feature. In his personal diaries he meticulously documented his loss of function and increasing anguish at his decline. Other health records suggest he also suffered from chronic hypertension. He had hoped that his symptoms were due to stress and leaving politics would aid his recovery, but instead found that "when I stepped out of Parliament in some mysterious fashion all my memories commenced to die or disappear". Contemporary doctors were unable to give him a clear diagnosis, other than a 1913 opinion of "hyperneurasthenia". Later writers have suggested vascular dementia, early-onset Alzheimer's disease, neurosyphilis, and Vitamin B12 deficiency from vegetarianism as possible causes of his illness.