Data collection

Information about the accident and injuries was collated on standard data sheets from ambulance, triage and emergency department records, and any in-patient notes, by a research worker who had previously been a senior trauma nurse in the department. Where possible, subjects were approached by a nurse and invited to take part; the remainder were sent information and questionnaires by post.

Patients completed a questionnaire which included questions on their initial emotional reactions to and memory of the accident, whether they thought they had been unconscious, or to blame for the accident, previous travel, and emotional and social adjustment. At 3 and 6 months after the accident they were also sent postal follow-up questionnaires, which included the Post-Traumatic Stress Symptom (PSS) scale (Reference Foa, Riggs and DancuFoa et al, 1993), the Hospital Anxiety and Depression (HAD) scale (Reference Zigmond and SnaithZigmond & Snaith, 1983) and questions about phobic travel anxiety derived from previous research (Reference Mayou, Bryant and DuthieMayou et al, 1993).

Measures

Statistical analysis

The relationship between unconsciousness and categorical variables was tested using the χ² test. Analysis of variance was used for the continuous variable ‘age’. Most of the scores on the variables measuring emotional reaction to the accident were rather skewed, so the Kruskal-Wallis one-way analysis of variance was used.

Head injury

Of the 1148 respondents, 261 (23%) were rated as having a minor head injury and 25 (2%) had had fractures. Twelve were investigated by computed tomography (CT) scan, of whom four were reported as abnormal.

Evidence of minor traumatic brain injury

Loss of consciousness

There were 124 respondents (11%) who reported they had been unconscious and 144 (13%) who were not sure - a total of 268. Review of the records suggested that only two of the 874 patients who indicated on the self-report questionnaire that they had not been unconscious had, in fact, been observed by others to be unconscious. Of those who said they had been unconscious, only 19 (15%) had been definitely, and 29 (23%) probably, unconscious as indicated by recorded evidence from bystanders and rescuers. In most of the remainder, rescue and emergency department notes clearly cited evidence that subjects had not lost consciousness although there were some comments about ‘confusion’ (Table 2).

Table 2 Patients' reports of unconsciousness and clarity of memories by emergency medicine specialist's rating of loss of consciousness (participants at baseline n=1148)

Emergency physician's rating	Definitely unconscious		Probably unconscious		Not unconscious
	n	(%)	n	(%)	n	(%)
Patient thought he/she had been unconscious
Yes	19	(70)	29	(64)	76	(7)
Not sure	6	(22)	13	(29)	125	(12)
No	2	(7)	3	(7)	869	(81)
Not known					6
Patient's memory of the accident
Clear	2	(7)	5	(11)	791	(74)
Patchy	13	(48)	24	(53)	249	(23)
None	12	(44)	16	(36)	28	(3)
Not known					8

Subjects classified as having been unconscious reported the accident as less frightening, felt less angry and were less likely to accept blame for the accident (Table 3). These subjects were also more likely to report themselves as numb and dazed in the first questionnaire immediately after the accident.

Table 3 Post-accident reactions of participants by loss of consciousness

Post-accident reaction	Definitely unconscious			Probably unconscious			Not unconscious			P 1
	Mean	s.d.	CI	Mean	s.d.	CI	Mean	s.d.	CI
Memory of accident (1-3)	2.37	0.63	2.1-2.6	2.24	0.65	2.1-2.4	1.29	0.5	1.26-1.32	<0.001
Unconscious (pt) (1-3)	1.37	0.63	1.1-1.6	1.42	0.62	1.2-1.6	2.74	0.58	2.71-2.78	<0.001
Frightening (1-4)	2.30	1.35	1.8-2.8	2.11	1.21	1.8-2.5	2.90	1.04	2.8-3.0	<0.001
Not to blame (1-3)	2.31	0.79	2.0-2.6	2.46	0.81	2.2-2.7	2.59	0.70	2.5-2.6	<0.05
Angry (0-4)	0.85	1.38	0.3-1.4	0.83	1.05	1.2-1.4	1.29	1.43	1.2-1.4	<0.05
Guilty (0-4)	0.73	1.31	0.2-1.3	0.66	1.09	0.3-1.0	0.43	0.94	0.4-0.5	NS
Numb (0-4)	1.62	1.47	1.0-2.2	1.20	1.08	0.8-1.5	0.86	1.11	0.8-0.9	<0.01
Dazed (0-4)	1.38	1.20	0.9-1.9	0.95	1.05	0.6-1.3	0.63	0.93	0.6-0.7	<0.001
Anxious (0-4)	1.08	1.02	0.7-1.5	1.39	1.36	1.0-1.8	1.32	1.29	1.2-1.4	NS

Unconsciousness was not associated with subsequent involvement in compensation proceedings. Claims were pursued by 36% of those definitely unconscious, 52% of those probably unconscious and 45% of those not unconscious.

Amnesia

Many of those for whom there was definite medical evidence of unconsciousness reported that they had no memories of the accident (44%), but two (7%) reported that they could remember the accident clearly and 13 (48%) described patchy memories (Table 2). Most reported continuing amnesia for parts of the accident at 3 months and 1 year (Table 4). Emergency department medical records rarely recorded the duration of post-traumatic amnesia, but review of medical notes and subjects' comments suggest that amnesia was usually brief and that many subjects had memories for events shortly before and after the road accident. Amnesia was also less frequent in those who had not suffered any head injury.

Table 4 Frequency of psychological symptoms at 3 months and 1 year by loss of consciousness

Symptom (0-3)	Definitely unconscious			Probably unconscious			Not unconscious			P 1
	Mean	s.d.	CI	Mean	s.d.	CI	Mean	s.d.	CI
3 months
Cannot remember bits	2.48	0.87	2.1-2.9	1.69	1.15	1.3-2.1	0.50	0.91	0.4-0.6	<0.001
Irritability	0.90	1.09	0.4-1.4	0.38	0.55	0.2-0.6	0.54	0.87	0.5-0.6	NS
Loss of concentration	1.33	1.35	0.7-2.0	0.56	0.80	0.3-0.9	0.48	0.80	0.4-0.5	<0.01
1 year
Cannot remember bits	1.48	1.29	0.9-2.1	1.38	1.21	0.9-1.8	0.36	0.79	0.3-0.4	<0.001
Irritability	0.67	1.02	0.2-1.1	0.41	0.80	0.1-0.7	0.44	0.79	0.4-0.5	NS
Loss of concentration	1.10	1.22	0.5-1.7	0.56	0.91	0.2-0.9	0.42	0.77	0.4-0.5	<0.01

Amnesia without traumatic loss of consciousness

It was common for patients who had not suffered any head injury to report that their memories of the accident were ‘patchy’. There were 28 subjects (2% of the eligible sample) who had no memory of the accident but who were thought not to have suffered any unconsciousness; only two-thirds were drivers. Five of these had suffered head injury above the hairline; of these it is possible that at least two subjects had been briefly unconscious, and three were described in notes as having been ‘confused’. Six more suffered facial injuries, one of whom may have been unconscious and two of whom were ‘confused’. In 17 there were clear written ambulance or emergency department records of their not being unconscious at any time. In these cases, examination of records suggested that other reasons - medical, psychological dissociation, alcohol intoxication and concerns about prosecution - could have been important causes: medical (diabetes, epilepsy), 2; fell asleep, 1; alcohol intoxication, 3; alcohol intoxication+later conviction, 8; alcohol+‘confusion’, 1; prosecution+‘confusion’, 2.

Twenty-one of the 28 subjects who, without loss of consciousness, had no memory of the accident at baseline replied at 3 months; three said they could now clearly remember the accident. At one year four out of the 19 who replied had full memories.

Psychological complications at 3 and 12 months

Post-traumatic stress disorder

Table 5 shows the main psychiatric syndromes at 3 months and 1 year in those who were definitely and probably unconscious and those who were not unconscious. PTSD was significantly more common at 3 months among those who had been definitely unconscious than in the remainder. Specific symptoms in each category of PTSD criteria were checked in those who had been unconscious as well as the symptoms of being unable to remember the accident. However, there was no significant difference at 1 year. Examination of comments on questionnaires, the information from an interview subgroup and medical records all suggest that the intrusive memories of the unconscious patients usually related to events just before or shortly after the accident, including being rescued, receiving emergency treatment and then being rushed to hospital. Eleven of the 21 subjects who were amnesic without being unconscious and who replied at follow-up suffered PTSD during the year.

Table 5 Psychological outcomes by loss of consciousness

	Definitely unconscious		Probably unconscious		Not unconscious		χ2 P
	n	(%)	n	(%)	n	(%)
PTSD at 3 months							<0.05
No	11	(52)	30	(77)	617	(81)
Yes	10	(48)	9	(23)	179	(23)
PTSD at 1 year							NS
No	14	(67)	32	(86)	594	(83)
Yes	7	(33)	5	(14)	116	(17)
Travel anxiety at 3 months							NS
No	15	(71)	33	(85)	621	(78)
Yes	6	(29)	6	(15)	173	(22)
Travel anxiety at 1 year							NS
No	15	(68)	32	(86)	596	(84)
Yes	7	(32)	5	(14)	115	(16)
HAD case at 3 months							<0.05
No	13	(62)	35	(90)	638	(81)
Yes	8	(38)	4	(10)	146	(19)
HAD case at 1 year							NS
No	16	(76)	26	(70)	567	(80)
Yes	5	(24)	11	(30)	139	(20)

When we compared those with minor head injury (i.e. unconsciousness of less than 15 minutes) with those who had no head injury, there were no differences in psychological consequences.

We examined case notes for the 23 subjects with major brain injury (i.e. prolonged unconsciousness) excluded from the self-report study, of whom 14 had been assessed by the specialist neurological rehabilitation service and two by the psychiatric consultation service. Both these services routinely assess for symptoms of PTSD and travel anxiety. There were three clearly described cases of subsequent travel anxiety but no evidence that any subject had suffered PTSD. The numbers were too small for statistical analysis.

Frequency of head injury and unconsciousness

By combining figures for different numbers of subjects for the various categories of available data we can summarise prevalences.

Major or minor head injury occurred in 23% of all attenders between the ages of 17 and 69 over the 1-year period, of whom 39% were admitted.

Major traumatic brain injury with prolonged unconsciousness (in all cases five days or more) and post-traumatic amnesia occurred in 1.6%.

Minor traumatic brain injury, as defined by loss of consciousness of less than 15 minutes, was medically rated as definitely occurring in 2% of subjects and probably in a further 4%. Within this group unconsciousness and amnesia were usually very brief - seconds rather than minutes.

Minor traumatic brain injury

In accordance with clinical experience, the definition of minor traumatic brain injury with evidence of impairment of consciousness and post-traumatic amnesia was not easy. Patients were frequently uncertain about whether they had lost consciousness, and they substantially overestimated this as compared with evidence in emergency service records. It is clearly very difficult for subjects to distinguish brief unconsciousness, acute concussion and peritraumatic psychological dissociation. However, although most clinical records did refer specifically to lack of evidence of impaired consciousness, they inevitably underestimate transient impairment of consciousness which may not be witnessed or clearly described by the subject.

Brief amnesia is difficult to assess and may not always be due to brain injury. Memories were frequently reported as ‘patchy’ by those in whom there was no question of head injury, a probable reflection of psychological dissociation which is a frequent accompaniment of road accidents and other trauma (Reference MurrayMurray, 1997). There were no differences in psychological outcomes between those who had injury above the hairline and those with facial injury.

Despite the difficulties, we have defined a subgroup who suffered minor traumatic brain injury. Any failure to identify a small number of other patients who were unconscious is unlikely to have significantly affected our findings about the prevalence of later psychological complications.

Psychiatric complications

Discussion of the psychiatric complications needs to consider the considerable overlap in the symptom criteria for the disorders considered in this paper. Thus, many of the symptoms associated with the syndrome of chronic concussion are also symptomatic of other psychiatric disorders, including PTSD, anxiety and depression. It should be noted that being unable to remember parts of the accident was one of the 17 symptoms of PTSD. There were no differences in prevalence at 1 year in those symptoms often associated with concussion included in the HAD scale and the PSS scale, with the exception of difficulty in concentrating.

There were no documented cases of PTSD and only two cases of travel anxiety among the 23 subjects with major head injury who suffered prolonged unconsciousness (and were therefore excluded from our postal study). However, we found clear evidence that PTSD is at least as common in those who suffer brief unconsciousness as in those who were not unconscious.

Several explanations have been suggested in relation to subjects with clear evidence of post-traumatic amnesia. The intrusive memories may relate to events before or after the period of amnesia, there may be islands of preserved memory (Reference ParkerParker, 1996), or it may be that there are ‘implicit’ memories which result in “intensive psychological distress on exposure to internal or external cues that symbolise or resemble an aspect of a traumatic event” (DSM-IV) (Reference Bryant, Marosszeky and CrooksBryant et al, 2000). The higher prevalence of PTSD in our ‘definitely unconscious’ group suggests that ‘concussion’ may hinder information processing.

We should consider two further issues in relation to the present series. We should note that those who were definitely or probably unconscious differed from the remainder in terms of variables which we have found to predict later PTSD and other psychological consequences: the severity of injury and in several aspects of their initial response, including the degree to which the accident was seen as frightening, blame, anger and feeling guilty.

It is also important to note the small subgroup of patients who had not suffered unconsciousness but had no memories of the accident and who later suffered higher prevalences of PTSD than other subjects. A major factor appeared to be alcohol, which may impair memory and perhaps information processing. It also seemed probable that denial (conscious or unconscious) was common among those at risk of legal proceedings. This was most obvious in the case of complete amnesia reported by a driver who had been responsible for the death of a child and for whom there was extensive neurological and psychiatric documentation of clear consciousness throughout.

Psychological symptoms following traumatic amnesia/unconsciousness

Our findings can be compared with those in other reports. The conclusions are clearly at variance with our own previous conclusions from a series in which there were no cases of PTSD among the few subjects who were briefly unconscious. This should be seen as a chance finding in a much smaller series. Blanchard and colleagues (Reference Hickling, Gillen and BlanchardHickling et al, 1998) recruited subjects a number of weeks after accidents and relied on cognitive testing and self-report of unconsciousness. They found similar rates of PTSD among those who believed they had been unconscious and those who had not. Bryant and Harvey (Reference Bryant and HarveyBryant & Harvey, 1998; Reference Harvey and BryantHarvey & Bryant, 1998) studied admitted patients (not all of whom had suffered road accidents) who were assessed as having suffered transient brain injury, and found that 14% satisfied criteria for acute stress disorder, and 24% sastisfied criteria for PTSD among subjects whose amnesia lasted up to 24 hours. Post-concussive symptoms were more frequent in subjects who suffered PTSD (Reference Bryant and HarveyBryant & Harvey, 1999). Bryant et al (Reference Bryant, Marosszeky and Crooks2000) have recently reported PTSD following severe traumatic brain injury.

We have demonstrated the particular problems of assessment of minor impairment of consciousness and of brief periods of amnesia and raised issues which require further, more specific research. However, it is apparent that a significant subgroup of road traffic accident victims suffer minor traumatic brain injury and that the risk of subsequent psychiatric complications - including travel anxiety and PTSD - is at least as great as for those who do not suffer brain injury. Many symptoms are not specific for any particular psychiatric disorder. Symptoms associated with chronic concussion were not more common in the subjects with traumatic brain injury but were associated with the other psychiatric complications.

The findings indicate the need for routine recording of post-traumatic amnesia and have clinical implications for the understanding of the complexity of psychological complications.

They also contribute to the evidence base for medico-legal reporting on the significance of evidence of possible minor brain injury, unconsciousness and amnesia in relation to the aetiology of long-term psychological consequences.

CLINICAL IMPLICATIONS

• ▪ Patient report of brief unconsciousness is unreliable.

• ▪ Clinical recording of post-traumatic amnesia should be routine in all attenders with possible head injury.

• ▪ Brief unconsciousness is associated with increased risk of post-traumatic stress disorder.

LIMITATIONS

• ▪ No research assessment of head injury or post-traumatic amnesia at hospital attendance.

• ▪ Self-report follow-up only.

• ▪ Response rate at follow-up was 75% of participants at 3 months and 67% at 1 year.