One old woman perplexed her neighbours, and doctors, by her sudden change of temperament and behaviour every autumn. Once the clocks were changed, she would start hallucinating, suffering delusions and bursting out in fits of uncontrollable laughter at the most inappropriate moments during conversations. She also seemed to be confused all the time.
This happened three years in a row, and doctors thought they were dealing with an extreme case of seasonal affective disorder (SAD), a condition where people become depressed due to the shorter days and fewer hours of sunlight.
But the real reason was more pragmatic. It was discovered that the berries that grew on a bush next to her home were ripe for picking at around the time the clocks changed. She was helping herself to her neighbour's fruit without realising that the berries were Atropa belladonna - better known as deadly nightshade (Postgrad Med J, 2003; 79: 239-40).