 Through late 1967 and early 1968 , Barrett 's behaviour became increasingly erratic and unpredictable , partly as a consequence of his reported heavy use of psychedelic drugs , most prominently LSD . There is also much speculation that he suffered from schizophrenia . Once described as joyful , friendly , and extroverted , he became increasingly depressed and socially withdrawn , and experienced hallucinations , disorganized speech , memory lapses , intense mood swings , and periods of catatonia . Although the changes began gradually , he went missing for a long weekend and , according to several friends including Rick Wright , came back " a completely different person . " One of the striking features of his change was the development of a blank , empty , dead @-@ eyed stare ( referred to in Pink Floyd 's " Shine on You Crazy Diamond " with the line " now there 's a look in your eye like black holes in the sky " ) . He was unable to recognize old friends that he had known for years , and often did not know where he was . At one point , while on a tour of the city of Los Angeles , Barrett is said to have exclaimed , " gee , it sure is nice to be in Las Vegas ! " Many reports described him on stage , strumming one chord through the entire concert , or not playing at all . At a show at The Fillmore in San Francisco , during a performance of " Interstellar Overdrive " , Barrett slowly detuned his guitar . The audience seemed to enjoy such antics , unaware of the rest of the band 's consternation . Interviewed on Pat Boone 's show during this tour , Syd 's reply to Boone 's questions was a " blank and totally mute stare , " according to Nick Mason , " Syd wasn 't into moving his lips that day . " Barrett exhibited similar behaviour during the band 's first appearance on Dick Clark 's popular TV show American Bandstand . Although surviving footage of this appearance shows Barrett miming his parts of the song competently , during a group interview afterwards , when asked two questions by Clark , Barrett 's answers were terse , almost to the point of rudeness ( though , Clark noted , they had been flying non @-@ stop from London to Los Angeles ) . During this time , Barrett would often forget to bring his guitar to sessions , damage equipment and occasionally was unable to hold his pick . Before a performance in late 1967 , Barrett reportedly crushed Mandrax tranquilliser tablets and an entire tube of Brylcreem into his hair , which subsequently melted down his face under the heat of the stage lighting , making him look like " a guttered candle " . Nick Mason later disputed the Mandrax portion of this story , stating that " Syd would never waste good mandies " . 
