A serious deficiency in this vital nutrient can cause beriberi, which has the immediate symptom of severe lethargy.
en.wikipedia.org Clinical signs associated with infection are nonspecific and may include appetite loss, uncoordinated swimming, lethargy, coelomic distention, darkening skin color, petechiae, fin erosion, and death.
en.wikipedia.org The disorder is characterized by episodic periods of hypersomnia and lethargy.
en.wikipedia.org Side effects may include vomiting, diarrhea, lethargy, drooling, or uncoordination.
en.wikipedia.org These include recurrent headache, lethargy, diplopia, and blurred vision, particularly with exercise or fasting.
en.wikipedia.org