This paper analyses the influence of and possible interaction between
chronotype (Morning-types, Neither-types and Evening-types) and person
ality dimensions (neuroticism, extroversion and psychoticism) in the d
aily consumption of alcohol and psychostimulants (nicotine and caffein
e). In a sample of 537 subjects (257 men and 280 women), who were stud
ents and professionals with different but fixed work schedules, there
were significant differences among the chronotypes regarding the consu
mption of all the above. Evening-types consumed more alcohol, nicotine
and caffeine (coffee and cola), while Morning-types consumed more caf
feine from tea. Personality was only related to the consumption of col
a: the greater the neuroticism the higher the consumption of this beve
rage. Stimulant drinks showed various types of interaction with person
ality types, which revealed a complex pattern of group action. The res
ults stress the need to consider chronotype as a contributory psycholo
gical factor in a multi-causal model of consumption of psychoactive su
bstances.