# Abstract

 Stress-related illnesses are a growing health problem in the Western world; which also has economic significance for society. As a consequence; there is a growing demand for effective treatments. The study investigates the long-term efficacy of the Nacadia^®^ nature-based therapy (NNBT) by comparing it to the efficacy of a validated cognitive behavioral therapy, called STreSS. The study is designed as a randomized controlled trial in which 84 participants are randomly allocated between the treatments. Long-term efficacy is investigated through data extracts from the national database of Statistics Denmark on the sick leave and the health-care consumption. The results show that both the NNBT and the STreSS lead to a significant decrease in number of contacts with a general practitioner in the period from twelve months prior to treatment to twelve months after treatment; and, a significant decrease in long-term sick leave from the month prior to treatment to twelve months after treatment. The positive long-term effects provide validation for the NNBT as an efficient treatment of stress-related illnesses. # 3. Results Of the 83 participants allocated between the two treatments, 41 participants completed the NBT treatment and 40 participants completed the CBT treatment (see [Figure 1](#)). Four participants in the NBT were lost to follow-up because the correct personal identification number was not provided. Five participants were lost to follow-up in the CBT; four participants did not provide the correct personal identification number; and, one participant withdrew consent after the treatment. The results from the background questionnaire showed that the vast majority of participants were women (NBT: 82%, CBT: 82%) with a mean age of 47.9 in NBT and 44.9 in CBT \[[11](#)\]. The majority had a university bachelor degree or higher education (NBT: 76%, CBT: 68%). The categorization of participants with respect to socioeconomic status showed an even distribution between the two treatments; the majority of participants in both NBT and CBT were employed at the start of treatment (NBT = 20; CBT = 21), and a great number held a top-level position (NBT = 13; CBT = 12) ([Table 1](#)). A substantial proportion of participants were also registered as unemployed at treatment start (NBT = 18; CBT = 18). Of those, 17 participants from the NBT and 16 participants from the CBT were fired from work during the twelve months preceding the start of treatment. Moreover, one participant in the NBT and two participants in the CBT quit their job during that period. 

## 3.1. Sick Leave All of the participants were rated as incapacitated for work for at least three months prior to treatment start, as stated in the inclusion criteria, but not all participants were registered as being on sick leave in Statistics Denmark prior to treatment start ([Figure 2](#)). They were, instead, registered as receiving other rehabilitation benefits or as students. The sample distributions, representing the number of months of sick leave, expressed significant deviations from the normal distribution (*p* < 0.05). Efforts to establish normal distributions using various types of statistical transformations were unsuccessful. No significant change was found in the total number of months of sick leave for the participants in the period from twelve months before the treatment compared to the twelve months after the treatment for either the NBT or the CBT treatments (*p* > 0.05). [Figure 2](#) illustrates the continous increase in the number of participants on sick-leave in the twelve months up to the start of treatment and, similarly, the similar decrease in the number of participants on sick leave from the end of the treatment to twelve months after. A significant decrease was found between the participants on sick leave one month prior to treatment and in month twelve after treatment (NBT: *p* < 0.001; CBT: *p* < 0.01), ([Table 2](#)). 23 participants (77%) who were on sick leave prior to treatment and received the NBT treatment were not on sick leave twelve months after completing the treatment ([Table 2](#)). 15 participants (60%) who were on sick leave prior to treatment start and received the CBT treatment were not on sick leave twelve months after completing the treatment ([Table 2](#)). In total, 27 participants from the NBT group and 20 participants from the CBT group were not on sick leave after completing the treatment. 

## 3.2. Healthcare Consumption For the NBT and the CBT, there was a significant reduction in number of contacts with a GP twelve months after treatment as compared to the twelve months before treatment (NBT *p* ˂ 0.01; CBT *p* ˂ 0.05) ([Table 3](#)). The sizes of the effect were r = −0.396 (NBT) and r = −0.249 (CBT). In terms of the number of contacts, the median number of contacts with a GP is still much higher for the participants one year after the treatment for both the NBT and the CBT groups when compared to the adult population of Denmark as a whole (mean number of contacts = 5.95) \[[24](#)\]. (Because the sample did not show a normal distribution, it was decided to use the median value instead of the mean value, which is used in the national sample. Nevertheless, the two statistical measures are still comparable in terms of understanding the central tendency of the statistical scores). <figure> <p><img src="" /></p> <figcaption>Participant flow diagram.</figcaption> </figure> <figure> <p><img src="" /></p> <figcaption>The proportion of participants on sick leave from twelve months prior to twelve months after a treatment. (NBT: <em>n</em> = 34; CBT: <em>n</em> = 30). Note 1. The gap in the graph represents the treatment period; Note 2. Data from the register: AMRUN; variable; SOC_STATUS_KODE was not available for 2016; therefore, data on three participants in NBT and five participants in CBT are missing.</figcaption> </figure> ::::table-wrap

ijerph-15-00137-t001_Table 1

::: caption
Socioeconomic classification of participants.
:::

Socioeconomic Classification NBT (*n* = 37) CBT (*n* = 35)

______________________________________________________________________

Employee---ground level 2 5
Employee---intermediate level 3 3
Employee---top level 13 12
Chief executive 1 0
Self-employed 1 1
Unemployed 18 18
Student 2 3
Other compensation services/job training 3 0

Note 1. Classification based on the register: AMRUN; variable;
SOC_STATUS_KODE; Note 2. Some participants were registered under several
codes in the AMRUN register at treatment start (NBT = 6 participants,
CBT = 7 participants).:::: ::::table-wrap
ijerph-15-00137-t002_Table 2

::: caption
Participants' sick-leave status from the month prior to treatment
compared to twelve months after the treatment (NBT: *n* = 34; CBT: *n* =
30).
:::

Treatments Point in Time Sick-Leave Status Month 12 after the Treatment

______________________________________________________________________

Not on Sick Leave On Sick Leave\
NBT (*n* = 34) 1 month before the treatment * Not on sick leave 4 0
On sick leave 23 7\
CBT (*n* = 30) 1 month before the treatment * Not on sick leave 5 1
On sick leave 15 9

- As the AMRUN register data is only available on a monthly basis, the
  starting point for the analysis was decided to be the month prior to the
  date of the treatment start; Note 2. Data from the register: AMRUN;
  variable; SOC_STATUS_KODE was not available for 2016; therefore, data on
  three participants in NBT and five participants in CBT are missing.:::: ::::table-wrap
  ijerph-15-00137-t003_Table 3

::: caption
Number of contacts with a general practitioner from twelve months before
treatment to twelve months after treatment (NBT: *n* = 37; CBT: *n* =
35).
:::

Treatment Point in Time Median Max. Min. Sign.

______________________________________________________________________

NBT (*n* = 37) Before 18 42 1 *p* = 0.001 \*\*\*\*\*\*
After 13 67 0\
CBT (*n* = 35) Before 21 103 6 *p* = 0.04 \*\*\*\*\*
After 14 35 5

- *p* < 0.05; \*\* *p* < 0.01.::::


Extracted trial result:
Outcome: Months of sick leave (continuous)
Intervention: Nacadia® nature-based therapy
Comparator: Cognitive behavioral therapy
Intervention group size: 37
Comparator group size: 35
Notes: Numerical values were not given for this outcome.