While many other things will cause the symptoms listed below, our research has found that these problems increase when shift workers work night shifts.

Mental Symptoms

Increased Irritability and Being Moody.
Its noted especially by partners that shift workers become more irritable after working night shifts. Our survey found that relationship break up was higher in shift workers and major causes cited were irritability or being "cranky" and days of bad moods.

Overly Emotional.

"Snapping or losing it" is another symptom reported by shift workers, and this was frequently followed by tears. Trying to comfort shift workers under stress only added to the problem and then created a problem for management. How do you manage an overly emotional worker who wants left alone?

Too Sensitive and Defensive.

Night shift workers increased level of stress made them too sensitive and defensive. For example the slightest criticism would be perceived as esteem bashing and led to disputes over small details. Or as one manager put it "getting all worked up over nothing."

Contrary behaviour.

Some workers were so stressed with night shift work that they became easily upset and were prone to seeing problems that were not really there. When asked to do certain tasks would frequently do something different and then argue that they were right and that management had a problem! These workers required a lot of management time in calming them down and trying to point out their contrary behaviour.


Forgetting to clock in or out and forgetting to do quality checks are two examples we found in our survey. Also many small tasks that are done automatically during the day were forgotten at night and the impact of all the small tasks not done at night caused major problems.

Comments on Mental Symptoms

From the above description it shows that stressed night shift workers can almost be unmanageable. Some academics have suggested that counselling and even therapy sessions to help shift workers deal with shift lag. Considering the mental state of a stressed out shift worker this approach would be very hard to implement.

Physical Symptoms


Being worn out and tired for days after night shifts, generally accompanied by a lack of concentration and motivation, especially for any activity that requires effort or skill. But even simple daily activities can become harder.

Loss of Energy and Sex Drive.

Shift workers in our survey reported a lack of energy for doing all normal activities they used to do before working night shifts. These included activities like; gardening, home maintenance and recreational sports. Also their sex drive dropped, but since it does for most of us as we get older this may or may not be attributable to shift work.

Broken Sleep after shifts.

Working during the hours of midnight to five am disrupts your circadian rhythms (normal wake and sleep cycle) and this can cause you to wake during your next sleep and then want to fall asleep during the next shift. Your inbuilt circadian rhythms have been disturbed, and it can take several days for the body to readjust. Broken sleep stops the shift worker getting quality sleep which delays any recovery from shift lag.


Increased constipation and fluid retention was reported by night shift workers in our survey. Other studies into shift work have reported similar findings.

Stomach problems.

An increase in stomach problems was reported by night shift workers. But some of the problems were attributed to night shift workers not eating properly. This suggests that this is one area that management of night shift workers can be improved. Insisting on adequate food for workers during night shifts. Mind you if a night shift worker has an upset stomach they may not be keen on eating. Then of course they are being contrary!

Dehydration, Dry Mouths and Increases in Colds and Flu's.

This can cause headaches, dry skin and nasal irritation, and make you more susceptible to any colds, coughs, sore throats and flu that are floating around in the work place. Our survey of night shift workers reported a greater number of sick days being taken with night shift workers suffering from colds, coughs, sore throats and flu more than those workers who didn't work night shifts.

Other Shift Work Medical Problems

Moore-Ede and Richardson in their paper called "Medical Implications of Shift-Work" showed that shift lag complaints fell into three specific areas:

1. Sleep-Awake Disorders.

Difficulties in falling asleep.
Difficulty staying asleep.
Chronic insomnia.
Increased use of sleeping pills.
Difficulty in staying awake at work.

One study reported that between one third and two thirds of shift workers report they fall asleep at least once a week on the job. And this occurs, because of the chronic cicadian phase disruption, not only during the night shift but also during the day and evening shifts.

2. Gastrointestinal Disorders.

General Gastric Discomfort.
Increased pectic ulcer disease, but this is only becomes significant after five years of continuous shift work.
Alcohol and tobacco consumption, known as factors in pectic ulcers are also higher in shift workers.

3. Cardiovascular Disorders.

Increase in cardiovascular disease, especially acute myocardial infarction.
Comperatore and Krueger in their paper called "Circadian rhythm desynchronosis, jet lag, shift lag, and coping strategies" found that among night shift workers, the immunological functions of lymphocytes in peripheral blood show a circadian variation and are lowered at night.

Gastrointestinal diseases such as gastric or duodenal ulcers occur more frequently among these workers. Shift workers, in general, complain more frequently of respiratory and motor organ disorders, shortage of quality sleep, increased fatigued levels, and lapses in performance.

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