a study of cancer patients, Vainio et al found no
significant effect of morphine on "...intelligence,
vigilance, concentration, fluency of motor reactions,
or division of attention. Of the neural function
tests, reaction times (auditory, visual, associative),
thermal discrimination, and body sway with eyes
open were similar in the two groups; only balancing
ability with closed eyes was worse in the morphine
group. These results indicate that, in cancer patients
receiving long-term morphine treatment with stable
doses, morphine has only a slight and selective
effect on functions related to driving."
et al found hydromorphone to have no effect on circular
lights, digit symbol substitution, and serial math
tasks or card-sorting tasks. Oxycodone, a mu-opioid
receptor agonist, was found to cause "increased
reaction time and impaired vigilance, attention,
body balance and coordination of extraocular muscles".
& Zacny reported "Psychomotor
impairment was ... and absent with morphine (which)...
produced dose-dependent decreases in pupil size.."
In an earlier study, Zacny et al found "morphine
had no effect on psychomotor functioning."
in healthy non-using volunteers.
et al, studying patients receiving high-dose morphine
therapy, found "Vigilance/attention,
psychomotor speed, and working memory were significantly
impaired in chronic nonmalignant pain patients."
In a study of cognitive and psychomotor function,
O"Neill et al reported: "Morphine
had one major effect, which was to increase the
accuracy of responding on the choice reaction time
task, at every assessment. Morphine produced some
sporadic effects in other tests and an increase
in subjective calmness. These data show that oral
morphine may enhance performance in some measures
of cognitive function", in an earlier
study of cancer pain management O"Neill had
reported "opioids do have effects
on cognitive and psychomotor function, and although
many of these effects diminish once the patient
is on a stable dose... the relationship between
measurable effects and the performance of everyday
tasks such as driving is unclear."
et al found morphine and codeine "...did
not affect performance on Maddox-Wing, digit-symbol
substitution, coordination, auditory reaction, reasoning,
and memory tests. Dose-related decreases in pupil
size (miosis) were observed following codeine and
morphine. ...These results suggest that oral codeine
and morphine ... have only modest effects on mood,
produce few side effects, and do not impair performance."
Zacny et al found "morphine
produced minimal psychomotor impairment.",
and that "morphine "...did
not affect performance on the Digit Symbol Substitution
Test." However by contrast Petry
at al found "Morphine produced
significant dose-dependent effects in DSST performance...
and pupil diameter."
in occasional drug users, whereas Zacny et al, studying
healthy non-using volunteers, concluded "Some
aspects of psychomotor performance (reaction time,
Digit Symbol Substitution Test and Maddox Wing)
were impaired by morphine; however, eye-hand coordination
was not. Miosis was induced by morphine. Most effects
of morphine were dose-related, some effects peaked
soon after morphine injection (e.g., increased stimulated
and high ratings) and dissipated gradually, whereas
other effects did not peak until later into the
session (sedation or exophoria). Our results are
fairly consistent with other studies examining morphine
effects in healthy volunteers, and also indicate
that the profile of morphine effects differ between
healthy volunteers and those with a history of opiate
et al, studying healthy volunteers, found "morphine
produced significant impairment at 1 hour on tests
of secondary memory retrieval (delayed word recall
and picture recognition sensitivity). CFFT was reduced
for the whole observation period (6 h) achieving
statistical significance at 4 hours. Morphine 15
mg produced a significant improvement in accuracy
on the choice reaction time test at the 2, 4 and
6 h assessments. These results show minimal impairment
of cognitive and psychomotor function after single
oral doses of morphine and with possible improvement
in one test." However, also with
healthy volunteers, Kerr et al reported "morphine...
caused significant impairments of some but not all
elements of cognitive and motor function. The time
needed to encode and process serially presented
verbal information increased and the ability to
maintain low consistent levels of force decreased
during the morphine infusion. We also assessed verbal
recall 3 hours after the morphine and saline infusions.
Delayed recall of information presented during the
morphine infusion was significantly impaired. Our
results demonstrate that morphine can interfere
with cognitive and motor performance at plasma drug
concentrations within the usual therapeutic range."
In a general review of the effects of painkillers
on occupational health, Payne concluded "all
classes of analgesics may impair... neuropsychiatric
functioning, which may influence job performance
in specific instances."
et al found "Morphine did not
impair psychomotor function (Trieger Dot Test (TDT)
and... Continuous Performance Test (CPT))"
Saddler at al compared the effects of alcohol and
morphine, finding "Ethanol
produced a significantly greater deterioration in
motor skills", with no effect of
morphine on reaction time.
& Nicholson studied the effects of codeine on
visuo-motor coordination, dynamic visual acuity,
critical flicker fusion, digit symbol substitution,
complex reaction time and subjective mood. They
reported "The effect on visuo-motor
coordination was limited and was dose related and
linear, and performance was altered on visuo-motor
coordination with 60 and 90 mg codeine, and on dynamic
visual acuity with 90 mg codeine (P less than 0.05).
No other effect of codeine was detected."
Saarialho-Kere et al found "Codeine
... failed to affect performance in objective tests
(body sway, digit symbol substitution, flicker fusion,
Maddox wing, nystagmus) "
et al, studying the effect of cold-water immersion
on the effects of morphine among naive users found
"Morphine impaired psychomotor
performance during one of the warm-water immersions,
but not during the cold-water immersions."
In a comparison study of the cognitive effects of
morphine and hydromorphone, "morphine
had less adverse consequences",
Beauford et al found no significant effect of morphine
on psychological test scores.
butorphanol in a high dose was found to "impair
psychomotor performance for up to 2 h, and produce
subjective effects for up to 3 h. The smaller dose
had no psychomotor-impairing effects, but had subjective
effects (including increased ratings of "sleepy").
All three active drug conditions included miosis
of the research involving the cognitive effects
of opiates has focussed on methadone maintenance
patients. Methadone has been found to adversely
affect cognitive ability, specifically memory impairment,
and also "information processing,
attention, short-term visual memory, delayed visual
memory, short-term verbal memory, long-term verbal
memory and problem solving."
et al.reported "heroin abusers
were impaired in learning the... intra-dimensional
shift component... tests of spatial working memory...
failed to show significant improvement between two
blocks of a sequence generation task after training
and additionally exhibited more perseverative behavior
on this task... profoundly... impaired on a test
of pattern recognition memory sensitive to temporal
lobe dysfunction.", and Eiber et
al noted "Opiate addicts showed
a decrease in episodic autobiographical memory but
an increase in semantic affective memory and objective
studies have investigated the effect of maternal
use during pregnancy on cognitive function of children,
mostly finding no effects once social circumstances
are controlled for, Goddard et al finding "childrens'
behaviour and cognitive skills were not adversely
affected", while Fabris et al found
"No long-term neurologic or
cognitive deficits are directly associated with
heroin or methadone use"
et al, studying patients with dual diagnosis of
psychiatric disorders and drug dependence, reported
"Heroin addicts reported that
heroin improved some of their psychiatric symptoms
and all of their cognitive dysfunctions."
Studying groups of individuals dependent on different
drugs and controls, Amir et al found heroin addicts
to make more errors in tests of cognitive impairment
studies have investigated cognitive impairment among
drug users infected with HIV, however few have attempted
to associate impairment with drug use whilst controlling
for HIV status, and most consider the effects to
be due to the virus rather than the drug. Del Pesce
et al found HIV infection was associated with cognitive
impairment in intravenous drug users compared to
seronegative users. Silberstein et al reported "seropositive
IVDAs may show evidence of impaired neuropsychological
function even in the absence of AIDS related symptoms
and are consistent with the hypothesis of the early
neurotropism of HTLV." Concha et
al, studying neuropsychological performance of drug
users, reported "Effects of
the frequency of reported past use of marijuana,
heroin, cocaine, barbiturates, and alcohol were
not statistically associated with performance on
& Galliani, using Rorschachs ink blots, found
long-term heroin addicts to perform worse than addicts
of shorter duration, considering their results to
"support the hypothesis that
cognitive functioning is impaired along with addiction
time" Roszell et al, comparing patients
receiving antidepressants and methadone maintenance,
noted "There were no significant
differences between groups on cognitive measures."
Miller reported "A neuropsychological
review of systems is likely to show a pattern of
impairment in substance abusers that involves the
integration of different cognitive functions for
effective problem solving."
et al found that a group of heroin addicts performed
better on the "positive Digit Span scatter"
test than neurotic/depressive patients, whilst Lombardo
et al found no differences in cognitive function
between low and medium-dose methadone patients.
However Gritz et al reported "Methadone
subjects performed significantly poorer on several
tests of learning and immediate recall compared
to abstinent subjects."