Here are the corrected sentences with the underlined parts corrected:

The discovery (41. discovered) that a member of your family is sleepwalking may be alarming (42. alarming) but it is not an uncommon phenomenon. Both adults and children sleepwalk, however, it is more common among children. Sleepwalking is not a psychological disorder (43. disorder) as some may think. Nor is there any connection (44. connection) between dreams and sleepwalking. The explanation which experts give for sleepwalking is that it is mainly due to being tired (45. tired) and under a lot of stress. Anxiety (46. Anxiety) (48. possesses) the (49. darkness) (47. pressure) at work or at school or even a loss of a favorite could trigger it off. Sleepwalkers move easily around the house, sometimes opening drawers as if searching for something. It is difficult to wake up a sleepwalker and it is considered unwise (50. unwise) because it can cause great distress. The following morning, he doesn't usually remember anything.