Senility
Senility was a mental deterioration that affected the elderly. Among the more notable victims was Ambassador Sarek just before he died in 2368. ()

In 2369, Counselor Deanna Troi related a disturbing encounter to Commander William T. Riker with Sev Maylor, the supposed mother of Ambassador Ves Alkar. She stated that she frightened her and that she sensed feelings from her that were out of proportion, malevolent and evil. To this, Riker responded that she was old, sick and probably senile, and that they might all go that way one day. However, unknown to anyone at the time, Alkar was actually using Maylor as a receptacle for his negative emotions and she was in fact not elderly at all, only 30 years old. ()

That same year, Els Renora stated to Commander Benjamin Sisko and Ilon Tandro during the trial of the Dax symbiont on Deep Space 9 that she wanted the proceedings to move swiftly and expected to be there until "supper, not senility." ()

In 2370, Beverly Crusher feigned indignation when a visiting Wesley requested his own quarters aboard the  by saying, "There comes a time in a young man's life when he doesn't want to stay with his poor senile mother." ()

In 2377, when the  was split into 37 timeframes, Commander Chakotay encountered Seska in a timeframe set in 2373, when she and a party of Kazons had temporarily taken control of the ship. In order to bring the ship into sync with normal time, it was necessary to emit a warp pulse, and he tried to enlist her help in doing this. Seska, however, tried to turn the plan to her own advantage and implied that Chakotay had become senile, stating "Men just get more distinguished as they get older. A few lines here, a little grey there, it adds character. Too bad their minds start to go." ()

In the anti-time future, Jean-Luc Picard was suspected of having senility within the 2390s. This suspicion influenced his credibility with others when Picard attempted to warn them about the anti-time eruption. ()

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Psychological conditions