Mental disorders, including cognitive and behavioural impairment, alcohol and substance misuse (ILO/IMO Guidelines Appendix E F00-99)

Impairment and risks

Adverse effects on personal performance through changes to perception, cognition, affect/mood, risk taking and thought processes. In some cases there is also impairment of movement and co-ordination.

These impairments sometimes have constant effects on an individual's capabilities. Where these take the form of lack of perception of limitations, suspicion, aggression or risk taking they can pose direct dangers to others and to vessel operations. More commonly they lead to erratic observation and analysis of the surroundings or to inhibition of learnt responses to external clues.

Episodic impairment of the sorts noted above that may interfere with safety-critical tasks is more common. Recurrences may be part of the natural history of the disease or either be attributed to work-related provoking factors such as overload, tiredness or a managerial climate perceived as harsh or inconsistent or to non-occupational causes such as relationship or financial problems.

The majority of relapses are not directly safety critical but lead to an ineffective or disturbed member of the crew. Violent behaviour is rare. Removal to onshore care may be needed for assessment and treatment.

Both diagnosis and the pattern of the condition in the individual are predictors or the probability and nature of future episodes. The boundary between the normal and abnormal is often a matter of perspective rather than clinical diagnosis, hence where the person has insight their self-evaluation of the condition is important, but can be difficult to elicit under the conditions of an employment related medical.

In addition to the well characterised forms of mental ill-health there are a number of people who, either because of unstable behaviour patterns or because of a repeated response to working in the constrained situation of a vessel, demonstrate traits that make them unsafe or unreliable seafarers.

Medications used to treat mental health problems frequently have side effects that can interfere with safe working. There is often a trade-off between the consequences of the condition and those of the medication used to control it.


Rationale and justification

  • The diagnosis of mental health problems differs from that for most other forms of ill-health as the identification of signs and symptoms has a large interpretative component. In many situations the boundary between the limits of normal and a definable case is indeterminate. This makes for uncertainty in quantification of relationship between conditions and risks and recurrence rates.
  • Psychiatric illness is associated with several specific areas of impairment that may be relevant to work at sea:
    • impaired information processing ability: attention, concentration, memory
    • reduced sustained attention, ie vigilance
    • impaired visual-spatial functioning with increased latency of motor responses
    • poor impulse control, including increased risk taking
    • poor judgement, including a reduced ability to predict and anticipate
    • reduced problem solving ability
    • indecisiveness.
  • There is evidence of unsafe behaviour associated with several conditions: dementia, the hypomanic phase of bipolar disorder, alcohol and drug misuse, personality disorders with aggressive or impulsive components. In addition the impairing effects of some medications used to treat mental health problems increase risk, and this is often exacerbated if there is alcohol or other drug misuse. Some delusions and hallucinations in psychotic illness can also alter the perception of reality in ways that creates risk.
  • A number of more common conditions can lead to impaired or limited performance, without any well-characterised increased safety risk. They may also, because of mood changes, cause tensions within the working group. There may be a trade off between the potential adverse effects of the condition and the side effects of medications used to control it. Examples include: anxiety, depression, obsessive behaviour, and the during the periods between exacerbations in those with psychotic illnesses.
  • The time course and risk of recurrence varies widely. For instance anxiety or depression that is a reaction to an external event such as a death or breakdown of a relationship normally resolves, as do such symptoms related to unsatisfactory working relationships when these have been resolved. Where there is a pattern of repeated episodes or where there are no clear provoking factors impairment is likely to be longer lasting and may fluctuate over a period of months or years. Many personality disorders are relatively stable traits, but their expression can often be related to provoking events. Psychotic illness, once a pattern of recurrences is established is likely to continue with such a pattern, often with a similar mode and speed of worsening on each occasion. Bipolar disorders commonly show a pattern of periodic swings from depression to hypomania and these tend to become more severe with time.
  • Medication, especially for depression and psychotic illness can reduce the probability and severity of recurrences, but sometimes at a cost of continuing side effects. Decisions to cease medication can be difficult and in addition there can be expected to be some increase in risk of recurrence on cessation. Other treatments such as psychotherapy and cognitive behavioural therapy can be effective and are also widely used. Some require continuing access to the therapist once the formal course is completed.
  • Proof of 'cure' is normally only by observation with lack of recurrences over a suitable period. The frequency of permanent freedom from a condition varies with diagnosis and prior duration of illness. For alcohol and drug misuse testing for the substance or for its effects can be used to monitor abstention but reversion to a pattern of misuse is relatively common.
  • The demands of work at sea, especially the effects of fatigue, poor management or perceived injustice can have an adverse effect on mood, provoke mental distress (stress) and exacerbate pre-existing conditions. The strain of emergencies at sea can also lead to similar ill-effects.
  • Many of the more fixed traits, such as personality disorders, dyslexia, learning difficulties and attention deficit hyperactivity disorder (ADHD) may cause problems during training and subsequently. Good vocational guidance can prevent expectations of a seafaring career being raised and then destroyed by failure during the training period.
  • Violent behaviour is rare, but may occur because of disinhibition, for instance in aggressive personality disorders, from alcohol or from combinations of alcohol and drugs in the presence of prior mental health problems. Mis-perceptions from delusions or hallucinations, including those during withdrawal from alcohol (DTs) or drugs, can also lead to violent behaviour. Personal distress, withdrawal from social contact or non-dangerous aberrant behaviour is much more common. Unless there is a clear and remediable provoking factor it will need medical assessment to clarify and manage the risk by making a diagnosis and instituting any required treatment.


Alcohol-specific rationale and justification

Note: – most of the available studies on safety critical performance relate to road vehicle and industrial accidents. Many of the findings can be extrapolated to work at sea. There are numerous maritime accident investigation reports that show similar patterns of impairment in seafarers, but a lack of population data.

  • Long term excessive drinking leads to deficits in cognition especially executive functions such as planning and prioritising tasks and attention, with impairment of visual-spatial judgements. Difficulty shifting and sustaining focus and inability to filter out distractions, as well as reduced self-regulation of impulsive actions are common. Peripheral neuropathies may also impair sensory input and motor actions. Other long-term life-shortening sequelae, such as cirrhosis of the liver and oesophageal varices occur.
  • Elevated blood alcohol levels, even to moderate levels in volunteers, are associated with complex changes in cognitive and motor performance, which do not keep in step with each other, with a more rapid return of motor skills than of cognitive ones as blood alcohol levels decline from their peak. It is not clear whether similar patterns occur in heavy drinkers who have developed a degree of tolerance to the effects of alcohol, at least on motor performance.
  • Road safety data suggest that tolerance to the effect of alcohol does not protect against accidents. The self-belief among regular drinkers that they are better adapted to drinking and driving compared with the occasional user of alcohol is not supported by any evidence.
  • Overall there is very good evidence that the road crash rate in problem drinkers, that is those who have a history of convictions for drink/drive offences, is elevated.
  • The determinants for progression from a 'problem drinker' with recurrent offences/crashes to a person who develops long-term sequelae from alcohol dependence are not clear although progression occurs in a significant proportion of convicted drink drivers.
  • The relationships between alcohol misuse and dependence are not clear. There is evidence of a 'hardcore' group of alcohol using repeat offenders, but they appear to represent one part of a spectrum of alcohol use, which includes a variety of traits leading to misuse and/or dependency.
  • In the driving population as a whole there is a well documented correlation between blood/breath alcohol levels and crash risk. There is no clear threshold below which impairment does not occur.
  • The impairing effects of medications with psychoactive or sedating effects and non-prescribed drugs such as cannabis and those of alcohol, interact with each other to produce more severe impairment than would be the case from either acting alone.
  • Both alcohol and drugs will increase the impairing effects of sleepiness in both those deprived of sleep and in those with sleep disorders.


Clinical assessment and decision taking

Cognitive, behavioural and mental health conditions, including misuse or dependency on alcohol or drugs, are among the most difficult risks to assess during a clinical consultation. An employment related medical is a setting where non-disclosure is frequent because disclosure is seen as jeopardising work prospects. If the seafarer is concerned about the result it can also be a tense interaction that may worsen anxiety or any limitations on social functioning.

Problems may become apparent from exploration of the person's past medical history. They may be suspected because of the responses to questions elicited during the assessment or concerns may have been passed to the examining doctor by others prior to the assessment. The purpose of the assessment is not to conduct a formal psychiatric diagnostic interview but to explore all the available information and the intuitive perceptions of the clinician to decide whether there is significant impairment, what its consequences are likely to be and to determine the need for a more specialised report before deciding on fitness.

Questioning about mental ill-health can be traumatic for the person being assessed and it is likely that relatively neutral questions that enable an assessment of history and affect to be made from several different perspectives will reveal most at the early stages, with more probing questioning, for instance about failed personal relationships or suicidal thoughts, left until near the end of the assessment.

There is a wide range of questionnaires available for determining current mental state and mood. None are specific enough to be used as the basis for taking decisions on fitness. In the case of alcohol misuse there are well validated questionnaires, such as the WHO 'AUDIT' instrument that can aid the detection of problems, but only if truthfully completed.

At the end of the consultation the examiner should have obtained an account of any past contact with health services because of mental or cognitive problems and have formed a view on the person's

  • Mood
  • Memory
  • Thought processes
  • Concentration
  • Agitation
  • Presence of psychotic symptoms
  • Behavioural disturbance
  • Side effect of any medication
  • Likely future changes to the present state from recurrence or exacerbation of an existing condition.


From this information and using the condition-specific guidance below and other reference sources they should either themselves form a view on:

a) the nature and probability of any risks to others and to vessel operations
b) risks to the individual
or establish that further details and opinions are needed from:
c) corroborating information from the person's general practitioner
d) specialist psychiatric or psychological assessment.

Information about behaviour, diagnosis and any past patterns of mental health impairment needs to be gathered from as many sources as possible to help decision taking. Past patterns while at sea can be particularly important. Where this is obtained from employers or other seafarers, consent and confidentiality issues need to be carefully considered as do the motives of anyone who volunteers information or opinions.


While the decision aid below may assist, a large measure of personal judgement is needed in concluding the appropriate fitness category for those with mental health, behavioural, cognitive and related forms of impairment.


  • High risk of recurrence and severe impairment – unfit to work at sea. e.g. more than one episode of psychosis or bipolar disorder, severe depression, major personality disorder with impulsive or aggressive features, history of recurrent failure to cope with work at sea. Unresolved alcohol or drug misuse problem
  • Medium risk of recurrence and impairment – limited fitness, restriction of duties, distance from care or with time limitation. Distant history of severe mental ill-health with no recent recurrences. Anxiety or depression that has not fully resolved. Recently resolved alcohol or drug misuse problem.
  • Low risk of recurrence and non-disabling impairment – fit. Reactive episode of anxiety or depression, now resolved. Minor degrees of abnormal affect or abnormal personality trait. Any mental health or substance misuse problem that has not been clinically apparent in the last five years.
  • Risk of recurrence is likely to be increased at the time when any medication is reduced or stopped. Ideally any changes to medication should be made at the start of a period of several weeks leave. Where this is not possible and it comes to the attention of the Approved Doctor then some temporary restriction on duties may need to be considered.


Condition-specific guidance

Note: psychiatric labels may be given for a variety or reasons, such as the medicalisation of failure to progress at school. Any reported diagnosis needs to be considered critically and not necessarily taken at face value.


  • Schizophrenic and delusional disorders
    Features can include: severe disturbances to thought processes, delusions and hallucinations, continuing impairment between acute episodes, a high probability of recurrence and the frequently impairing effects of the medications. These mean that many of those with such conditions will be unfit to start or return to seafaring. Freedom from recurrence and medication for several years may permit a return (2 above). Single psychotic episodes with external provocation e.g. from infection or medication have a good prognosis and, once a period of six months has elapsed to confirm that the episode was one-off normal duties can be started or resumed.

  • Alcohol misuse and dependency
    The use of alcohol (as well as drugs for non-therapeutic purposes) is a disciplinary as well as a medical issue for seafarers. This is covered by IMO and ILO instruments as well as by national regulations. Many maritime employers have company policies on alcohol and drug use and screening. The health professional has a role to play in determining fitness for service at sea, in screening, in investigation of incidents and in the treatment and rehabilitation of seafarers who misuse or who are dependent on alcohol.
    Single episodes of excessive alcohol use will not normally be relevant to fitness assessment but a repeated pattern indicates a high risk of future episodes of impairment that will be safety-critical if they occur at sea or shortly before embarkation. There is also likely to be associated behavioural change and impaired cognition from repeated misuse of dependency, as well as a risk of long term complications such as liver disease and oesophageal varices. Taking a valid history of alcohol intake and problems usually requires questions to be asked several times and in different ways to assess the consistency of reply. Intuitive assessment of affect and the truthfulness of replies is important. An intuitive view on the person's insight about their pattern of alcohol use and its effects can influence decisions on further investigation or on categorisation of fitness. Some simple question sets are available. The WHO AUDIT set being the best known internationally (Alcohol Use Disorders Identification Test (AUDIT) WHO/MSD/MSB/6a World Health Organization. Second Edition 2001).

    Liver function and MCV testing is justified to help evaluate suspicions of persistent misuse and have a baseline level for the future assessments. Results can also be used to demonstrate the reality of harm to the individual.
    In some case there may not appear to be sufficient risk to justify insistence on a formal treatment programme before returning to sea but there is either a continuing high level of intake or repeated episodes of drunkenness while on leave. Here the use of time limited certificates and re-assessment at three to six monthly intervals with re-certification dependent on stated compliance with and agreed pattern of alcohol use in a person with insight of with steady or improving liver function and MCV results can be appropriate.
    Relapses during and after formal and informal treatment regimes are common, hence continuing surveillance is justified. The adverse effects of alcohol use for vessel safety when the master of senior officer has a problem mean that a higher standard of proof of long-term control of alcohol use can be justified. Use of alcohol and drugs or medication together can be very severely impairing and this needs to be considered when assessing fitness.

  • Drug misuse and dependency
    The use of drugs for non-therapeutic purposes is usually illegal and is a disciplinary as well as a medical issue for seafarers. This is covered by IMO and ILO instruments as well as by national regulations. Many maritime employers have company policies on drug use and screening. The health professional has a role to play in determining fitness for service at sea, in screening, in investigation of incidents and rehabilitation of seafarers who misuse or who are dependent on drugs.
    The same problems of disclosure and assessment as those for alcohol are relevant, but will be heightened by the illegality of drug use and especially of the supply of drugs for use by others. Drug screening is widely used and may be a condition of employment but is not a requirement during statutory seafarer medicals. It can, however, be justified if there is a reasonable clinical suspicion of adverse effects from drug use. If drug use is disclosed or identified then compliance with a formal treatment programme is required in most cases and certainly where highly addictive substances are used (opiates, cocaine). The use of substances such as stimulants and cannabis during leave periods need not be a reason for unfitness, but the commonly used drug screens continue to detect cannabis for several weeks after use and this can cause practical and administrative problems if they are found. Any use while at sea indicates a marked lack of insight and a requirement for demonstrated abstinence before return to work at sea is acceptable.
    Opiate addicts are frequently maintained on either more easily controlled forms of opiate such as methadone or on antagonists such as naltrexone. Methadone has directly impairing effects and this means that use while at sea is not acceptable. Antagonist use can be accepted if the other criteria for control are met.
    In many addicts multiple drug use is the norm and abstinence from one substance may mean that others are substituted. Co-use of alcohol is also frequent and for substances such as cannabis this can cause far more severe impairment than either substance on its own.

  • Mood (affective) disorders
    The most severe forms, especially bipolar disorders with a hypomanic phase when judgement and insight are lost, are a significant safety risk. The pattern of mood swings is persistent and can become ever more extreme. Once there have been three clear episodes of major mood swings a return to a stable affect is unusual. ???(2 above). A long period away from safety critical responsibilities and with speedy access to health care is needed and return to sea is only justifiable after a several years free from symptoms and usually off medication.
    Severe depression with withdrawal, major sleep disturbances and suicidal ideas is frequently recurrent. Recurrences can be prompted by interpersonal difficulties. Several years stability are needed before working at sea.
    Less severe forms of anxiety/depression are compatible with continuing to work at sea, once treatment has been stabilised, shown to be effective and any medications used do not cause impairment. Where the symptoms are reactive to external events the prognosis is good once they have been resolved. However if the events relate to conflicts at work these will need to be resolved before improvement can be expected.

  • Phobic anxiety disorders
    Here a particular stimulus excites severe and distressing arousal. Treatment can be very effective. Where the phobia is to a stimulus unlikely to be met at sea and it has been treated then fitness can be assumed. However if it relates to events that can occur on board or it is a generalised response to a wide and ill-defined set of provoking factors it is likely to be incompatible with work in responsible jobs or other than close to shore.

  • Obsessive compulsive disorders
    The symptoms of these conditions are likely to interfere with working and living arrangements in aboard. An individual assessment of the severity and consequences of symptoms needs to be made.

  • Disorders of personality
    Most are lifelong traits and if they involve significant aggression, impulsiveness, lack of perception of risks, lack of insight into the effects of actions on others then they are unlikely to be compatible with work at sea.

  • Disorders of psychological development
    Autism and Asperger's syndrome impair inter-personal interactions. As these are critical to work at sea individual assessment is needed but the more severe forms of these conditions are incompatible with fitness for seafaring.

  • Hyperkinetic disorders
    Attention Deficit Hyperactivity Disorder (ADHD) is a relatively common diagnosis in boys with educational difficulties. It is cared for within a paediatric framework and there is often a discontinuity in care in the mid-teens. Where it is severe it is unlikely to be compatible with work in any senior jobs at sea where vigilance is needed. Individual assessment is needed. As the commonly used medication (ritalin) is also used as a drug of abuse safe custody on board may be a problem.

  • Brain damage and organic disease
    Many causes will be excluded from seafaring because of the primary disease e.g. liver or kidney failure, epilepsy. Late effects of infection (meningitis and encephalitis) and head injury need to be considered in terms of the present state assessment of cognition and behaviour (1 above) and separately in terms of seizure risk.

  • Eating disorders
    Eating disorders with severe loss of muscle mass or with self induced emesis are unlikely to be compatible with work at sea. Such disorders are often associated with other psychological traits which could impair performance and reliability. A specialist assessment prior to a decision on fitness should be considered where the condition has been active in the last five years.

  • Self harm
    This is often a marker of other psychological and behavioural problems. However it may also be a cult activity. A specialist assessment prior to a decision on fitness should be considered where the condition has been active in the last five years.

  • Dyslexia
    While not strictly a mental health problem it is listed here because of its effects on learning and communication ability. Clinical assessment is largely irrelevant as it is educational and communication ability that are impaired. Fitness certification decisions should not be based on reported dyslexia. There may be occasions when the person examined admits to the condition. They need to be advised to discuss with their employer or training institution, or if seen prior to seafaring to be advised that, while help may be available in college, they are likely to find that any inability to write or communicate effectively will make a seafaring career as an officer very limited.

  • Psychologically or temperamentally unsuited for work at sea
    This is a relatively common mental health problem presenting to maritime doctors. There is often a history of episodes of inability to perform tasks that are within the capability of other crew members. This may be associated with stress, anxiety and depressive symptoms and these will frequently be attributed to external factors such as the personalities of other crew members or to home circumstances. While on the borderline of medical and managerial responsibilities referral for medical advice is common and this may be at the time of a statutory medical. The decision on fitness can take account of a history of inability to perform duties based on evidence of health related impairment. If this is not apparent then the decision on future employment is a managerial one, where the doctor may act as an adviser to the employer, provided that standards of ethics and confidentiality are respected and that the seafarer is referred by the employer for such an assessment because of concerns about performance, but examining doctor should not use the medical certificate of fitness to provide an easy solution for the employer.


Suggested framework for decision taking

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